HyperText Markup Language -- 2.0
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Abstract
The HyperText Markup Language (HTML) is a simple markup language
used to represent hypertext documents that are portable from one
platform to another. HTML documents are SGML documents with generic
semantics that are appropriate for representing information from a
wide range of applications. HTML markup can represent hypertext
news, mail, documentation, and hypermedia; menus of options;
database query results; simple structured documents with graphics;
and hypertext views of existing bodies of information.
HTML has been in use by the World Wide Web (WWW) global information
initiative since 1990. This specification roughly corresponds to
the capabilities of HTML in common use prior to June 1994. It is
defined as an application of ISO Standard 8879:1986 Information
Processing Text and Office Systems; Standard Generalized Markup
Language (SGML).
The "text/html; version=2.0" Internet Media Type (RFC 1590) and
MIME Content Type (RFC 1521) is defined by this specification.
Contents
(@@ I'll regenerate this eventually)
1. Introduction
1.1 Purpose
The HyperText Markup Language (HTML) is a simple markup language
used to create hypertext documents that are portable from one
platform to another. HTML documents are SGML documents with generic
semantics that are appropriate for representing information from a
wide range of applications. HTML has been in use by the World-Wide
Web (WWW) global information initiative since 1990. This
specification corresponds to the capabilities of HTML in common use
prior to June 1994 and referred to as "HTML 2.0".
This specification defines HTML as an application of ISO Standard
8879:1986 Information Processing Text and Office Systems; Standard
Generalized Markup Language (SGML). SGML provides a formal
definition of the HTML syntax in the form of a Document Type
Definition (DTD).
This specification also defines HTML as an Internet Media Type [7]
and MIME Content Type [4] called "text/html", or
"text/html; version=2.0". As such, it defines the semantics of the
HTML syntax and how that syntax should be interpreted by user agents.
1.2 Levels of Conformance
Version 2.0 of HTML introduces a distinction between levels of
conformance:
Level 0
Indicates the minimum conformance level. When writing Level 0
documents, authors can be confident that the rendering at
different sites will reflect their intent.
Level 1
Includes Level 0 features plus features such as highlighting and
images.
Level 2
Includes all Level 0 and Level 1 features, plus forms.
1.3 Terminology
The HTML specification uses these words with precise meanings:
attribute
A name/value pair: part of an element which is often used
to specify a characteristic quality of the element, other than
type or content.
character
An atom of information, for example a letter or a number.
Graphic characters have associated glyphs, where as control
characters have associated processing semantics.
character encoding
A mapping from sequences of octets to sequences of characters
from a character repertiore; that is, a sequence of octets and a
character encoding determines a sequence of characters.
character number
A number that determines a character, as per some character set.
character repertoire
A finite set of characters. The range of the mapping defined
by a character set.
character set
A mapping of a subset of the integers onto a character
repertoire. That is, for some set of integers (usually of
the form {0, 1, 2, ..., N} ), a character set and an integer
in that set determine a character. Conversely, a character
and a character set determine the character's number (or,
in rare cases, a few character numbers).
conforming HTML user agent
A user agent that conforms to this specification in its
treatment of the Internet Media Type "text/html; version=2.0"
document type definition (DTD)
A DTD is a collection of declarations (entity, element,
attribute, link, map, etc.) in SGML syntax that defines the
components and structures available for a class (type) of
documents.
element
A component of the hierarchical structure defined by the
document type definition; it is identified in a document
instance by descriptive markup, usually a start-tag and an end-
tag.
entity
A text entity, or some other data with an associated notation or
interpretation; for example, a sequence of octets associated
with an Internet Media Type.
MIME entity
a head and body. The head is a collection of name/value fields,
and the body is a sequence of octets. The head defines the
content type and content transfer encoding of the body.
SGML document
A set of entities, including the document entity, which is
a text entity that conforms to the grammar specified in the SGML
standard.
HTML document
An SGML document conforming to the HTML document type definition.
HTTP
The Hypertext Transfer Protocol [3] is the primary application-
level protocol for the transfer of documents via the World-Wide
Web.
(document) instance
The document itself including the actual content with the actual
markup. Can be a single document or part of a document instance
set that follows the DTD.
markup
Text added to the data of a document to convey information about
it. There are four different kinds of markup: descriptive markup
(tags), references, markup declarations, and processing
instructions.
MIME
The Multipurpose Internet Mail Extensions [4] provide the
ability to transfer non-textual data, such as graphics, audio
and fax, via Internet mail.
minimally conforming HTML user agent
A user agent that conforms to this specification in its
treatment of the Internet Media Type "text/html; level=0;
version=2.0"
SGML
Standard Generalized Markup Language [12] (see also [9] and [6])
is a system for describing docyment types and markup languages
to represent them.
tag
Markup that delimits an element. A tag includes a name which
refers to an element declaration in the DTD, and may include
attributes.
text entity
A finite sequence of characters. A text entity typically takes
the form of a sequence of octets with some associated character
encoding, transmitted over the network or stored in a file.
user agent
A component of a distributed system that presents an interface
and processes requests on behalf of a user; for example, a www
browser or a mail user agent.
URI
A Universal Resource Identifier [1] is a formatted string that
serves as an identifier for a resource, typically on the
Internet. URIs are used in HTML to identify the destination of
hypertext links, the source of in-line images, and the object of
form actions. URIs in common use include Uniform Resource
Locators (URLs) [2] and Relative URLs [5].
WWW
The World-Wide Web is a hypertext-based, distributed information
system created by researchers at CERN in Switzerland. Users may
create, edit or browse hypertext documents.
<URL:http://www.w3.org/>
1.4 Imperatives
may
The implementation is not obliged to follow this in any way.
must
If this is not followed, the implementation does not conform to
this specification.
shall
If this is not followed, the implementation does not conform to
this specification.
should
If this is not followed, though the implementation officially
conforms to the specification, undesirable results may occur in
practice.
typical
Typical rendering is described for many elements. This is not a
mandatory part of the specification but is given as guidance for
designers and to help explain the uses for which the elements
were intended.
2. HTML as an Application of SGML
HTML is an application of ISO Standard 8879:1986 -- Standard
Generalized Markup Language (SGML) [12]. SGML is a system for
defining structured document types and markup languages to
represent instances of those document types. The SGML declaration
for HTML and the HTML document type definitions (DTDs) are provided
in Section 12.
The term "HTML" refers to both the document type defined here and
the markup language for representing instances of this document
type.
If this specification and the SGML standard conflict,
the SGML standard is definitive.
2.1 SGML Documents
An HTML document is an SGML document; that is, a set of entities,
including the document entity, which is a text entity that conforms
to the grammar specified in the SGML standard. The first production
of that grammar separates an SGML document into three parts: an
SGML declaration, a prologue, and an instance.
For the purposes of this specification, the prologue is a DTD. This
DTD describes another grammar: the start symbol is given in the
doctype declaration; the terminals are data characters and tags,
and the productions are determined by the element declarations. The
instance must conform to the DTD, that is, it must be in the
language defined by this grammar.
The SGML declaration determines the lexicon of the grammar. It
specifies the document character set; which determines a character
repertoire that contains all characters used in all text entities
in the document, and the character numbers associated with those
characters.
The SGML declaration also specifies the syntax character set of the
document, and a few other parameters that bind the abstract syntax
of SGML to a concrete syntax. This concrete syntax determines how
each text entity is mapped to a sequence of terminals in the grammar
of the prologue.
For example, consider the following document:
<!DOCTYPE html PUBLIC "-//IETF//DTD HTML 2.0//EN">
<title>Parsing Example</title>
<p>Some text. <em>*wow*</em>
By application convention, the SGML declaration is the one given in
section 13.2. Hence the document character set is ISO-8859-1(@@)
and the markup "*" represents an asterisk character.
The instance is regarded as the following sequence of terminals:
TITLE start tag
data characters: "Parsing Example"
TITLE end tag
P start tag
data characters "Some text. "
EM start tag
"*wow*"
EM end tag
The start symbol of the DTD grammar is HTML, and the productions
are given in the public text identified by "-//IETF//DTD HTML
2.0//EN", that is section 13.3@@. Hence the terminals abover parse
as:
HTML
|
\-HEAD, BODY
| |
\-TITLE \-P
| |
| \-<P>,"Some text. ",EM
| |
| \-<EM>,"*wow*",</EM>
\-<TITLE>,"Parsing Example",</TITLE>
2.2 HTML Lexical Syntax
The syntax character set for all HTML documents is ISO-646 (@@ full
name). A minimally conforming HTML user agent must support the SGML
declaration in section 13@@, which specifies ISO Latin 1 (@@full
name) as the document character set; it may support other SGML
declarations, in particular, SGML declarations with other document
character sets.
A complete discussion of the mapping of a sequence of characters to
a seqence of tags and data is left to the SGML standard. This
section is only a summary.
2.2.1 Data Characters
Any sequence of characters that do not constitute markup (see
"Delimiter Recognition," section @@@ of the SGML standard) are
mapped directly to strings of data characters. Some markup also
maps to data character strings. Numeric character references also
map to single-character strings, via the document character
set. Each reference to one of the general entities defined in the
HTLM DTD also maps to a single-character string.
For example,
abc<def => "abc","<","def"
abc<def => "abc","<","def"
Note that the terminating semicolon is only necessary when the
character following the reference would otherwise be recognized as
markup:
abc < def => "abc ","<"," def"
abc < def => "abc ","<"," def"
And note that an ampersand is only recognized as markup when it
is followed by a letter or number:
abc & lt def => "abc & lt def"
abc & 60 def => "abc & 60 def"
A useful technique for translating plain text to HTML is to replace
each '<', '&', and '>' by an entity reference or numeric character
reference as follows:
ENTITY NUMERIC
CHARACTER REFERENCE CHAR REf CHARACTER DESCRIPTION
& & & Ampersand
< < < Less than
> > > Greater than
Note: There are SGML features, CDATA and RCDATA, to allow
most "<", ">", and "&" characters to be entered without the
use of entity references. Because these features tend to be
used and implemented inconsistently, and because they
require 8bit characters to represent non-ASCII characters,
they are not used in this version of the HTML DTD.
2.2.1 Tags
Tags define the start and end of headings, paragraphs, lists,
character highlighting and links. Most HTML elements are identified
in a document as a start tag, which gives the element name and
attributes, followed by the content, followed by the end tag. Start
tags are delimited by "<" and ">"; end tags are delimited by "</"
and ">". An example is:
<H1>This is a Heading</H1>
Some elements only have a start tag without an end tag. For
example, to create a line break, you use the <BR> tag.
Additionally, the end tags of some other elements, such as
Paragraph (<P>), List Item (<LI>), Definition Term (<DT>), and
Definition Description (<DD>) elements, may be omitted.
The content of an element is a sequence of characters and nested
elements. Some elements, such as anchors, cannot be nested. Anchors
and character highlighting may be put inside other constructs. See
the HTML DTD for full details.
Note: The SGML declaration for HTML specifies SHORTTAG YES,
which means that there are other valid syntaxes for tags,
such as NET tags, "<EM/.../"; empty start tags, "<>"; and
empty end tags, "</>". Until support for these idioms is
widely deployed, their use is strongly discouraged.
2.2.2 Names
A name consists of a letter followed by up to 71 letters, digits,
periods, or hyphens. Element names are not case sensitive, but
entity names are. For example, <BLOCKQUOTE>, <BlockQuote>, and
<blockquote> are equivalent, whereas & is different from &.
In a start tag, the element name must immediately follow the tag
open delimiter "<".
2.2.3 Attributes
In a start tag, white space and attributes are allowed between the
element name and the closing delimiter. An attribute typically
consists of an attribute name, an equal sign, and a value (although
some attributes may be just a value). White space is allowed around
the equal sign.
The value of the attribute may be either:
o A string literal, delimited by single quotes or double quotes
and not containing any occurrences of the delimiting character.
o A name token (a sequence of letters, digits, periods, or
hyphens)
In this example, A is the element name, HREF is the attribute name,
and http://host/dir/file.html is the attribute value:
<A HREF="http://host/dir/file.html">
Note: Some historical implementations consider any occurrence
of the ">" character to signal the end of a tag. For
compatibility with such implementations, when ">" appears in an
attribute value, it should be represented with a numeric
character reference, such as in: <IMG SRC="eq1.jpg" alt="a
> b">
A useful technique for computing an attribute value literal for a
given string is to replace each quote and space character by an
entity reference or numeric character reference as follows:
ENTITY NUMERIC
CHARACTER REFERENCE CHAR REf CHARACTER DESCRIPTION
TAB 	 Tab
LF Line Feed
CR Carriage Return
  Space
" " " Quotation mark
& & & Ampersand
For example:
<IMG SRC="image.jpg" alt="First "real" example">
Note: Some historical implementations allow any character
except space or ">" in a name token. Attributes values must
be quoted only if they don't satisfy the syntax for a name
token.
The length of an attribute value (not the attribute value literal:
this is the result of stripping the quotes and replacing any
references).is limited to 1024 characters
Attributes with a declared value of NAME, such as ISMAP and
COMPACT, may be written using a minimized syntax. The markup:
<UL COMPACT="compact">
can be written using a minimized syntax:
<UL COMPACT>
Note: Some historical implementations only understand the
minimized syntax.
2.2.5 Comments
To include comments in an HTML document that will be eliminated in
the mapping to terminals, surround them with "<!--" and
"-->". After the comment delimiter, all text up to the next
occurrence of "-->" is ignored. Hence comments cannot be
nested. White space is allowed between the closing "--" and ">",
but not between the opening "<!" and "--".
For example:
<HEAD>
<TITLE>HTML Guide: Recommended Usage</TITLE>
<!-- $Id: Text.html,v 1.6 1994/04/25 17:33:48 connolly Exp$ -->
</HEAD>
Note: Some historical HTML implementations incorrectly consider
any ">" character to be the termination of a comment.
2.3 Example HTML Document
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML//EN">
<HTML>
<!-- Here's a good place to put a comment. -->
<HEAD>
<TITLE>Structural Example</TITLE>
</HEAD><BODY>
<H1>First Header</H1>
<P>This is a paragraph in the example HTML file. Keep in mind
that the title does not appear in the document text, but that
the header (defined by H1) does.</P>
<OL>
<LI>First item in an ordered list.
<LI>Second item in an ordered list.
<UL COMPACT>
<LI> Note that lists can be nested;
<LI> Whitespace may be used to assist in reading the
HTML source.
</UL>
<LI>Third item in an ordered list.
</OL>
<P>This is an additional paragraph. Technically, end tags are
not required for paragraphs, although they are allowed. You can
include character highlighting in a paragraph. <EM>This sentence
of the paragraph is emphasized.</EM> Note that the </P>
end tag has been omitted.
<P>
<IMG SRC ="triangle.xbm" alt="Warning:">
Be sure to read these <b>bold instructions</b>.
</BODY></HTML>
3. HTML as an Internet Media Type
An HTML user agent allows users to interact with resources which
have HTML representations. At a minimum, it must allow users to
examine and navigate the content of HTML Level 0 documents. Level 1
HTML user agents must be able preserve all formatting distinctions
represented in an HTML Level 1 document, and be able to
simultaneously present resources referred to by IMG elements. (they
may ignore some formatting distinctions or IMG resources at the
request of the user). Fully conforming HTML user agents, that is
Level 2 HTML user agents, must support form entry and submission.
3.1 text/html media type
This specification defines the Internet Media Type [7] (formerly
referred to as the MIME Content Type [4]) called "text/html". The
following is to be registered with IANA [8].
Media Type name: text
Media subtype name: html
Required parameters: none
Optional parameters: level, version, charset
Encoding considerations: any encoding is allowed
Security considerations: [Section 14]
The optional parameters are defined as follows:
Level
The level parameter specifies the feature set used in the
document. The level is an integer number, implying that any
features of same or lower level may be present in the document.
Levels 0, 1 and 2 are defined by this specification. Level 2 is
the default.
Version
To help avoid future compatibility problems, the version
parameter may be used to give the version number of the
specification to which the document conforms. The version number
appears at the front of this document and within the public
identifier of the HTML DTD. This specification defines
version 2.0.
Charset
The charset parameter (as defined in section 7.1.1 of RFC
1521 [4]) may be given to specify the encoding used to represent
the HTML document as a sequence of octets. The default value is
out of scope of this specification; but for example, it is
US-ASCII in the context of MIME mail, and ISO-8850-1 in the
context of HTTP.
3.2 HTML Document Represenation
A MIME entity with a content type of "text/html" represents an HTML
document, consisting of a single text entity. The charset parameter
(whether implicit or explicit) identifies a character encoding. The
text entity consists of the characters determined by this character
encoding and the octets of the body of the MIME entity.
The SGML declaration of the document is a function of the charset
parameter. If the charset parameter is US-ASCII or ISO-8859-1, the
SGML declaration in section 13@@ applies. Other charset parameter
values are reserved for future use.
NOTE: A generalized convention for mapping charset parameter values
to SGML declarations is expected to be specified in a future
version of this specification.
3.2.1 Conventional Handling of Undeclared Markup Errors
NOTE: To facilitate experimentation and interoperability between
implementations of various versions of HMTL, the installed base of
HTML user agents supports a superset of the HTML 2.0 language by
reducing it to HTML 2.0: markup in the form of a start tag or end
tag whose generic identifier is not declared is mapped to nothing
during tokenization. Undeclared attributes are treated similarly.
The entire attribute specification of an unknown attribute (i.e.,
the unknown attribute and its value, if any) should be ignored.
On the other hand, references to undeclared entities should be
treated as data characters.
For example:
<div class=chapter><h1>foo</h1><p>...</div>
=> <H1>,"foo",</H1>,<P>,"..."
xxx <P ID=z23> yyy
=> "xxx ",<P>," yyy
Let α and β be finite sets.
=> "Let α and β be finite sets."
Support for notifying the user of such errors is encouraged.
Information providers should keep in mind that this convention is
not binding: unspecified behaviour may result, as such markup is
not conforming to this specification.
3.2.1 Conventional Representation of Newlines and Record Delimiter Characters
SGML specifies that a text entity is a sequence of records, each
beginning with a record start character and ending with a record
end character (character number 10 13 respectively).
MIME specifies that a body of type text/* is a sequence of lines,
each terminated by CRLF, that is octets 10, 13.
NOTE: In practice, HTML documents are frequently represented and
transmitted using an end of line convention that depends on the
conventions of the source of the document; frequently, that
representation consists of CR only, LF only, or CR LF
combination. Hence the decoding of the octets will often result in
a text entity with some missing record start and record end
characters.
Since there is no ambiguity, HTML user agents are encouraged to
infer the missing record start and end characters.
An HTML user agent should treat end of line in any of its
variations as a word space in all contexts except
preformatted text. Within preformatted text, an HTML user agent
should expect to treat any of the three common representations of
end-of-line as starting a new line.
4. Document Structure Elements
To identify information as an HTML document conforming to this
specification, each document should start with the prologue:
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
Note: If the body of a text/html body part does not begin
with a document type declaration, an HTML user agent should
infer the above document type declaration.
HTML documents should also contain an <HTML> tag at the beginning
(immediately after the prologue) and an </HTML> tag at the end of
the file. Within those tags, an HTML document is organized as a
head and a body, much like a memo or a mail message. Within the
head, you can specify the title and other information about the
document. Within the body, you can structure text into paragraphs
and lists, as well as highlight phrases and create links, using
HTML elements.
Note: Technically, the start and end tags for HTML, Head,
and Body elements are omissible; however, this is not
recommended since the head/body structure allows an
implementation to determine certain properties of a
document, such as the title, without parsing the entire
document.
4.1 HTML Identifier
<HTML> ... </HTML> Level 0
The HTML identifier defines the document as containing HTML
elements. It contains only the Head and Body elements.
4.2 Head
<HEAD> ... </HEAD> Level 0
The head of an HTML document is an unordered collection of
information about the document. It requires the Title element
between <HEAD> and </HEAD> tags:
<HEAD>
<TITLE>Introduction to HTML</TITLE>
</HEAD>
4.3 Body
<BODY> ... </BODY> Level 0
The Body element identifies the body component of an HTML document.
Specifically, the body of a document may contain links, text, and
formatting information within <BODY> and </BODY> tags.
5. Document Metainformation Elements
5.1 Title
<TITLE> ... </TITLE> Level 0
Every HTML document must contain a Title element. The title should
identify the contents of the document in a global context, and may
be used in history lists and as a label for the window displaying
the document. Unlike headings, titles are not rendered in the text
of a document itself.
The Title element must occur within the head of the document, and
must not contain anchors, paragraph tags, or highlighting. Only one
title is allowed in a document.
Note: The length of a title is not limited; however, long
titles may be truncated in some applications. To minimize
this possibility, titles should be fewer than 64 characters.
Also keep in mind that a short title, such as Introduction,
may be meaningless out of context. An example of a
meaningful title might be "Introduction to HTML Elements."
5.2 Base
<BASE> Level 0
The Base element allows the URL [2] of the document itself to be
recorded in situations in which the document may be read out of
context. URLs within the document may be in a "partial" form
relative to this base address [5].
The Base element has one attribute, HREF, which identifies the
absolute base URL.
5.3 Isindex
<ISINDEX> Level 0
The Isindex element tells the user agent that the document is an
index. This means that the reader may request a keyword search on
the resource by adding a question mark to the end of the document
address, followed by a list of keywords separated by plus signs.
The Isindex element is usually generated by the network server from
which the document was obtained via a URI. The server must have a
search engine that supports this feature for the resource. If the
document URI is unknown to the user agent, <isindex> must be
ignored.
5.4 Link
<LINK> Level 0
The Link element indicates a relationship between the document and
some other object. A document may have any number of Link elements.
The Link element is empty (does not have a closing tag), but takes
the same attributes as the Anchor element.
Typical uses are to indicate authorship, related indexes and
glossaries, older or more recent versions, etc. Links can indicate
a static tree structure in which the document was authored by
pointing to a "parent" and "next" and "previous" document, for
example.
Servers may also allow links to be added by those who do not have
the right to alter the body of a document.
5.5 Meta
<META> Level 0
The META element is used within the HEAD element to embed document
metainformation not defined by other HTML elements. META elements
can be extracted by servers and/or clients for use in identifying,
indexing, and cataloging specialized document metainformation.
Although it is generally preferable to use named elements which
have well-defined semantics for each type of metainformation (e.g.
TITLE), the META element is provided for situations where strict
SGML parsing is necessary and the local DTD is not extensible. HTML
user agents may use the META element's content if they recognize
and understand the semantics identified by the NAME or HTTP-EQUIV
attributes, and may treat the content as metainformation (and not
render it) even when they do not recognize the name.
In addition, HTTP servers may wish to read the content of the
document HEAD to generate header fields corresponding to any
elements defining a value for the attribute HTTPEQUIV. Note,
however, that the method by which the server extracts document
metainformation is not part of this specification, nor can it be
assumed by authors that any given server will be capable of
extracting it. The META element only provides an extensible
mechanism for identifying and embedding document metainformation --
how it may be used is up to the individual server implementation
and the HTML user agent.
Attributes of the META element:
HTTP-EQUIV
This attribute binds the element to an HTTP header field. It
means that if you know the semantics of the HTTP header field
named by this attribute, then you can process the contents based
on a well-defined syntactic mapping, whether or not your DTD
tells you anything about it. HTTP header field names are not
case sensitive. If not present, the attribute NAME should be
used to identify this metainformation and the content should not
be used within an HTTP response header.
NAME
Metainformation name. If the NAME attribute is not present, the
name can be assumed to be equal to the value of HTTP-EQUIV.
CONTENT
The metainformation content to be associated with the given
name. If multiple META elements are provided with the same name,
their combined contents--concatenated as a comma-separated list--
is the value associated with that name.
Examples
If the document contains:
<META HTTP-EQUIV="Expires"
CONTENT="Tue, 04 Dec 1993 21:29:02 GMT">
<meta http-equiv="Keywords" CONTENT="Fred, Barney">
<META HTTP-EQUIV="Reply-to"
content="fielding@ics.uci.edu (Roy Fielding)">
then the server (if so configured) may include the following
headers:
Expires: Tue, 04 Dec 1993 21:29:02 GMT
Keywords: Fred, Barney
Reply-to: fielding@ics.uci.edu (Roy Fielding)
as part of the HTTP response to a GET or HEAD request for that
document.
When the HTTP-EQUIV attribute is not present, the server should not
generate an HTTP response header for the metainformation; e.g.,
<META NAME="IndexType" CONTENT="Service">
would never generate an HTTP response header, but would still allow
HTML user agent to identify and make use of that metainformation.
The Meta element should never be used to define information that
should be associated with an existing HTML element. An example of
an inappropriate use of the Meta element is:
<META NAME="Title" CONTENT="The Etymology of Dunsel">
Do not name an HTTP-EQUIV equal to a response header that should
normally only be generated by the HTTP server. Example names that
are inappropriate include "Server", "Date", and "Last-modified" --
the exact list of inappropriate names is dependent on the
particular server implementation. We recommend that servers ignore
any META elements which specify HTTP-equivalents which are equal
(case-insensitively) to their own reserved response headers.
5.6 Nextid
<NEXTID> Level 0
The Nextid element is a parameter read and generated by text
editing software to create unique identifiers. This tag takes a
single attribute which is the next document-wide alpha-numeric
identifier to be allocated of the form z123:
<NEXTID N=Z27>
When modifying a document, existing anchor identifiers should not
be reused, as these identifiers may be referenced by other
documents. Human writers of HTML usually use mnemonic alphabetical
identifiers.
HTML user agentss may ignore the Nextid element. Support for the
Nextid element does not impact HTML user agents in any way.
6. Data Characters
An HTML user agent should present the body of an HTML document as
a collection of typeset paragraphs and preformatted text. Except
for te PRE element, each block structuring element is regarded as
a paragraph by taking the data characters in its content and the
content of its descendent elements, concatenating them, and
splitting the result into words, separated by space, tab, or
record end characters (and perhaps hyphen characters). The
sequence of words is typeset as a paragraph by breaking it into
lines.
6.1 The ISO Latin 1 Character Repertiore
Conforming HTML user agents are required to support the US-ASCII
[10] or ISO-8859-1 [11] character encodings, and the @@fullname ISO
Latin 1 document character set.
The character repertiore shared by these two is known as Latin
Alphabet No. 1, or simply Latin-1. Latin-1 includes characters
from most Western European languages, as well as a number of
control characters. Latin-1 also includes a non-breaking space, a
soft hyphen indicator, 93 graphical characters, 8 unassigned
characters, and 25 control characters.
NOTE: Use the non-breaking space and soft hyphen indicator characters is
discouraged because support for them is not widely deployed.
In SGML applications, the use of control characters is limited in
order to maximize the chance of successful interchange over
heterogenous networks and operating systems. In HTML, only three
control characters are allowed: Horizontal Tab (HT, encoded as 9
decimal in US-ASCII and ISO-8859-1), Carriage Return, and Line Feed.
The HTML DTD references the Added Latin 1 entity set, to allow
mnemonic representation of Latin 1 characters using only the widely
supported ASCII character repertiore. For exaple:
Kurt Gödel was a famous logician and mathematician.
See Section 13.2 for a table of the "Added Latin 1" entities.
Each character in the document character set can be written as a
numeric character reference. This list, sorted numerically, is
derived from ISO-8859-1 8-bit single-byte coded graphic character
set:
REFERENCE DESCRIPTION
� -  Unused
	 Horizontal tab
Line feed
 -  Unused
  Space
! Exclamation mark
" Quotation mark
# Number sign
$ Dollar sign
% Percent sign
& Ampersand
' Apostrophe
( Left parenthesis
) Right parenthesis
* Asterisk
+ Plus sign
, Comma
- Hyphen
. Period (fullstop)
/ Solidus (slash)
0 - 9 Digits 0-9
: Colon
; Semi-colon
< Less than
= Equals sign
> Greater than
? Question mark
@ Commercial at
A - Z Letters A-Z
[ Left square bracket
\ Reverse solidus (backslash)
] Right square bracket
^ Caret
_ Horizontal bar (underscore)
` Acute accent
a - z Letters a-z
{ Left curly brace
| Vertical bar
} Right curly brace
~ Tilde
 -   Unused
¡ Inverted exclamation
¢ Cent sign
£ Pound sterling
¤ General currency sign
¥ Yen sign
¦ Broken vertical bar
§ Section sign
¨ Umlaut (dieresis)
© Copyright
ª Feminine ordinal
« Left angle quote, guillemotleft
¬ Not sign
­ Soft hyphen
® Registered trademark
¯ Macron accent
° Degree sign
± Plus or minus
² Superscript two
³ Superscript three
´ Acute accent
µ Micro sign
¶ Paragraph sign
· Middle dot
¸ Cedilla
¹ Superscript one
º Masculine ordinal
» Right angle quote, guillemotright
¼ Fraction one-fourth
½ Fraction one-half
¾ Fraction three-fourths
¿ Inverted question mark
À Capital A, grave accent
Á Capital A, acute accent
 Capital A, circumflex accent
à Capital A, tilde
Ä Capital A, dieresis or umlaut mark
Å Capital A, ring
Æ Capital AE dipthong (ligature)
Ç Capital C, cedilla
È Capital E, grave accent
É Capital E, acute accent
Ê Capital E, circumflex accent
Ë Capital E, dieresis or umlaut mark
Ì Capital I, grave accent
Í Capital I, acute accent
Î Capital I, circumflex accent
Ï Capital I, dieresis or umlaut mark
Ð Capital Eth, Icelandic
Ñ Capital N, tilde
Ò Capital O, grave accent
Ó Capital O, acute accent
Ô Capital O, circumflex accent
Õ Capital O, tilde
Ö Capital O, dieresis or umlaut mark
× Multiply sign
Ø Capital O, slash
Ù Capital U, grave accent
Ú Capital U, acute accent
Û Capital U, circumflex accent
Ü Capital U, dieresis or umlaut mark
Ý Capital Y, acute accent
Þ Capital THORN, Icelandic
ß Small sharp s, German (sz ligature)
à Small a, grave accent
á Small a, acute accent
â Small a, circumflex accent
ã Small a, tilde
ä Small a, dieresis or umlaut mark
å Small a, ring
æ Small ae dipthong (ligature)
ç Small c, cedilla
è Small e, grave accent
é Small e, acute accent
ê Small e, circumflex accent
ë Small e, dieresis or umlaut mark
ì Small i, grave accent
í Small i, acute accent
î Small i, circumflex accent
ï Small i, dieresis or umlaut mark
ð Small eth, Icelandic
ñ Small n, tilde
ò Small o, grave accent
ó Small o, acute accent
ô Small o, circumflex accent
õ Small o, tilde
ö Small o, dieresis or umlaut mark
÷ Division sign
ø Small o, slash
ù Small u, grave accent
ú Small u, acute accent
û Small u, circumflex accent
ü Small u, dieresis or umlaut mark
ý Small y, acute accent
þ Small thorn, Icelandic
ÿ Small y, dieresis or umlaut mark
7. Data Elements
7.1 Line Break
<BR> Level 0
The Line Break element specifies a line break in a paragraph or
preformatted text section. A new line should indent the same as
that of line- wrapped text.
Example of use:
<P> Pease porridge hot<BR>
Pease porridge cold<BR>
Pease porridge in the pot<BR>
Nine days old.
7.2 Horizontal Rule
<HR> Level 0
A Horizontal Rule element is a divider between sections of text
such as a full width horizontal rule or equivalent graphic.
Example of use:
<BODY>
...
<HR>
<ADDRESS>February 8, 1995, CERN</ADDRESS>
</BODY>
7.3 Image
<IMG> Level 0
The Image element is used to incorporate in-line graphics
(typically icons or small graphics) into an HTML document. This
element cannot be used for embedding other HTML text.
HTML user agents that cannot render in-line images ignore the
Image element unless it contains the ALT attribute. Note that some
HTML user agents can render linked graphics but not in-line
graphics. If a graphic is essential, you may want to create a link
to it rather than to put it in-line. If the graphic is not
essential, then the Image element is appropriate.
The Image element, which is empty (no closing tag), has these
attributes:
ALIGN
The ALIGN attribute accepts the values TOP or MIDDLE or BOTTOM,
which specifies if the following line of text is aligned with
the top, middle, or bottom of the graphic.
ALT
Optional text as an alternative to the graphic for rendering in
non-graphical environments. Alternate text should be provided
whenever the graphic is not rendered. Alternate text is
mandatory for Level 0 documents. Example of use:
<IMG SRC="triangle.xbm" ALT="Warning:"> Be sure to read these
instructions.
ISMAP
The ISMAP (is map) attribute identifies an image as an image
map. Image maps are graphics in which certain regions are mapped
to URLs. By clicking on different regions, different resources
can be accessed from the same graphic. Example of use:
<A HREF="http://machine/htbin/imagemap/sample">
<IMG SRC="sample.xbm" ISMAP>
</A>
SRC
The value of the SRC attribute is the URL of the document to be
embedded; only images can be embedded, not HTML text. Its syntax
is the same as that of the HREF attribute of the <A> tag. SRC is
mandatory. Image elements are allowed within anchors.
Example of use:
<IMG SRC="triangle.xbm">Be sure to read these instructions.
8. Character Format Elements
Character format elements are used to specify either the logical
meaning or the physical appearance of marked text without causing a
paragraph break. Like most other elements, character format
elements include both opening and closing tags. Only the characters
between the tags are affected:
This is <EM>emphasized</EM> text.
Character format tags may be ignored by minimal HTML applications.
Character format tags are interpreted from left to right as they
appear in the flow of text. Level 1 user agents must render
highlighted text distinctly from plain text. Additionally, EM
content must be rendered as distinct from STRONG content, and B
content must rendered as distinct from I content.
Character format elements may be nested within the content of other
character format elements; however, HTML user agents are not
required to render nested character format elements distinctly from
non-nested elements:
plain <B>bold <I>italic</I></B> may the rendered the same as
plain <B>bold </B><I>italic</I>
8.1 Semantic Format Elements
Note that typical renderings for semantic format elements vary
between applications. If a specific rendering is necessary -- for
example, when referring to a specific text attribute as in "The
italic parts are mandatory" -- a physical formating element can be
used to ensure that the intended rendered is used where possible.
Note that different sematic elements may be rendered in the same
way.
8.1.1 Citation
<CITE>...</CITE> Level 1
The Citation element specifies a citation, typically rendered as
italics.
8.1.2 Code
<CODE> ... </CODE> Level 1
The Code element indicates an example of code, typically rendered
in a monospaced font. This should not be confused with the
Preformatted Text element.
8.1.3 Emphasis
<EM> ... </EM> Level 1
The Emphasis element indicates typographic emphasis, typically
rendered as italics.
8.1.4 Keyboard
<KBD> ... </KBD> Level 1
The Keyboard element indicates text typed by a user, typically
rendered in a monospaced font. This is commonly used in instruction
manuals.
8.1.5 Sample
<SAMP> ... </SAMP> Level 1
The Sample element indicates a sequence of literal characters,
typically rendered in a monospaced font.
8.1.6 Strong
<STRONG> ... </STRONG> Level 1
The Strong element indicates strong typographic emphasis, typically
rendered in bold.
8.1.7 Variable
<VAR> ... </VAR> Level 1
The Variable element indicates a variable name, typically rendered
as italic.
8.2 Physical Format Elements
Physical format elements are used to specify the format of marked
text.
8.2.1 Bold
<B> ... </B> Level 1
The Bold element specifies that the text should be rendered in
boldface, where available. Otherwise, an alternative mapping is
allowed.
8.2.2 Italic
<I> ... </I> Level 1
The Italic element specifies that the text should be rendered in an
italic font, where available. Otherwise, an alternative mapping is
allowed.
8.2.3 Teletype
<TT> ... </TT> Level 1
The Teletype element specifies that the text should be rendered in
a fixed-width typewriter font.
9. Hypertext Elements
9.1 Anchor
<A> ... </A> Level 0
An anchor is a marked section of text that is the start and/or
destination of a hypertext link. Anchor elements are defined by the
<A> tag. The <A> tag accepts several attributes; at least one of
the NAME and HREF attributes is required.
Attributes of the <A> tag:
9.1.1 HREF
If the HREF attribute is present, the text between the opening and
closing anchor tags becomes hypertext. If this hypertext is
selected by readers, they are moved to another document, or to a
different location in the current document, whose network address
is defined by the value of the HREF attribute.
Example:
See <A HREF="http://www.hal.com/">HaL</A>'s information for more
details.
In this example, selecting "HaL" takes the reader to a document at
http://www.hal.com. The format of the network address is specified
in the URI specification for print readers.
With the HREF attribute, the form HREF="#identifier" can refer to
another anchor in the same document.
Example:
The <A HREF="#glossary">glossary</A> defines terms used in this
document.
In this example, selecting "glossary" takes the reader to another
anchor (i.e., <A NAME="glossary">Glossary</A>) in the same
document. The NAME attribute is described below. If the anchor is
in another document, the HREF attribute may be relative to the
document's address or the specified base address (see Section 5.2).
9.1.2 NAME
If present, the NAME attribute allows the anchor to be the target
of a link. The value of the NAME attribute is an identifier for the
anchor. Identifiers are arbitrary strings but must be unique within
the HTML document.
Example of use:
<A NAME="coffee">Coffee</A> is an example of ...
... An example of this is <A HREF="#coffee">coffee</A>.
Another document can then make a reference explicitly to this
anchor by putting the identifier after the address, separated by a
hash sign:
<A HREF="drinks.html#coffee">
9.1.3 TITLE
The TITLE attribute is informational only. If present, the TITLE
attribute should provide the title of the document whose address is
given by the HREF attribute. The TITLE attribute is useful for at
least two reasons. The HTML user agent may display the title of
the document prior to retrieving it, for example, as a margin note
or on a small box while the mouse is over the anchor, or while the
document is being loaded. Another reason is that documents that are
not marked up text, such as graphics, plain text and Gopher menus,
do not have titles. The TITLE attribute can be used to provide a
title to such documents. When using the TITLE attribute, the title
should be valid and unique for the destination document.
9.1.4 REL
The REL attribute gives the relationship(s) described by the
hypertext link from the anchor to the target. The value is a
whitespace-separated list of relationship names. Relationship names
and their semantics will be registered by the W3 Consortium. The
default relationship is void. The REL attribute is only used when
the HREF attribute is present.
9.1.5 REV
The REV attribute is the same as the REL attribute, but the
semantics of the link type are in the reverse direction. A link
from A to B with REL="X" expresses the same relationship as a link
from B to A with REV="X". An anchor may have both REL and REV
attributes.
9.1.6 URN
If present, the URN attribute specifies a uniform resource name
(URN) for a target document. The format of URNs is under discussion
(1995) by various working groups of the Internet Engineering Task
Force.
9.1.7 METHODS
The METHODS attributes of anchors and links provide information
about the functions that the user may perform on an object. These
are more accurately given by the HTTP protocol when it is used, but
it may, for similar reasons as for the TITLE attribute, be useful
to include the information in advance in the link. For example, the
HTML user agent may chose a different rendering as a function of
the methods allowed; for example, something that is searchable may
get a different icon.
The value of the METHODS attribute is a whitespace-separated list
of HTTP methods supported by the object for public use.
10. Block Structuring Elements
The following elements may be included in the body of an HTML
document:
10.1 Paragraph
<P> ... </P> Level 0
The Paragraph element indicates a paragraph. The exact indentation,
leading space, etc. of a paragraph is not defined and may be a
function of other tags, style sheets, etc.
Typically, paragraphs are surrounded by a vertical space of one
line or half a line. This is typically not the case within the
Address element and is never the case within the Preformatted Text
element. With some HTML user agents, the first line in a paragraph
is indented.
Example of use:
<H1>This Heading Precedes the Paragraph</H1>
<P>This is the text of the first paragraph.
<P>This is the text of the second paragraph. Although you do not
need to start paragraphs on new lines, maintaining this
convention facilitates document maintenance.</P>
<P>This is the text of a third paragraph.</P>
10.2 Preformatted Text
<PRE> ... </PRE> Level 0
The Preformatted Text element presents blocks of text in fixed-
width font, and so is suitable for text that has been formatted on
screen.
The WIDTH attribute specifies the maximum number of characters for
a line and allows an HTML user agent to select a suitable font and
indentation. The WIDTH attribute defaults to 80. Widths of 40, 80
and 132 characters should be presented optimally, with other widths
being rounded up.
Within preformatted text:
o Line breaks within the text are rendered as a move to the
beginning of the next line.
o The <P> tag should not be used. If found, it should be rendered
as a move to the beginning of the next line.
o Anchor elements and character highlighting elements may be used.
o Elements that define paragraph formatting (headings, address,
etc.) must not be used.
o The horizontal tab character (encoded in US-ASCII and ISO-8859-1
as decimal 9) must be interpreted as the smallest positive
nonzero number of spaces which will leave the number of
characters so far on the line as a multiple of 8. Its use is
not recommended however.
Note: References to the "beginning of a new line" do not
imply that the renderer is forbidden from using a constant
left indent for rendering preformatted text. The left indent
may be constrained by the width required.
Example of use:
<PRE WIDTH="80">
This is an example line.
</PRE>
Note: Within a Preformatted Text element, the constraint
that the rendering must be on a fixed horizontal character
pitch may limit or prevent the ability of the HTML
user agent to faithfully render character formatting
elements.
10.3 Address
<ADDRESS> ... </ADDRESS> Level 0
The Address element specifies such information as address,
signature and authorship, often at the top or bottom of a document.
Typically, an Address is rendered in an italic typeface and may be
indented. The Address element implies a paragraph break before and
after.
Example of use:
<ADDRESS>
Newsletter editor<BR>
J.R. Brown<BR>
JimquickPost News, Jumquick, CT 01234<BR>
Tel (123) 456 7890
</ADDRESS>
10.4 Blockquote
<BLOCKQUOTE> ... </BLOCKQUOTE> Level 0
The Blockquote element is used to contain text quoted from another
source.
A typical rendering might be a slight extra left and right indent,
and/or italic font. The Blockquote element causes a paragraph
break, and typically provides space above and below the quote.
Single-font rendition may reflect the quotation style of Internet
mail by putting a vertical line of graphic characters, such as the
greater than symbol (>), in the left margin.
Example of use:
I think the poem ends
<BLOCKQUOTE>
<P>Soft you now, the fair Ophelia. Nymph, in thy orisons, be all
my sins remembered.
</BLOCKQUOTE>
but I am not sure.
10.5 Headings
<H1> ... </H1> through <H6> ... </H6> Level 0
HTML defines six levels of heading. A Heading element implies all
the font changes, paragraph breaks before and after, and white
space necessary to render the heading.
The highest level of headings is H1, followed by H2 ... H6.
Example of use:
<H1>This is a heading</H1>
Here is some text
<H2>Second level heading</H2>
Here is some more text.
The rendering of headings is determined by the HTML user agent,
but typical renderings are:
<H1> ... </H1>
Bold, very-large font, centered. One or two blank lines above
and below.
<H2> ... </H2>
Bold, large font, flush-left. One or two blank lines above and
below.
<H3> ... </H3>
Italic, large font, slightly indented from the left margin. One
or two blank lines above and below.
<H4> ... </H4>
Bold, normal font, indented more than H3. One blank line above
and below.
<H5> ... </H5>
Italic, normal font, indented as H4. One blank line above.
<H6> ... </H6>
Bold, indented same as normal text, more than H5. One blank line
above.
Although heading levels can be skipped (for example, from H1 to
H3), this practice is discouraged as skipping heading levels may
produce unpredictable results when generating other representations
from HTML.
10.6 List Elements
HTML supports several types of lists, all of which may be nested.
10.6.1 Definition List
<DL> ... </DL> Level 0
A definition list is a list of terms and corresponding definitions.
Definition lists are typically formatted with the term flush-left
and the definition, formatted paragraph style, indented after the
term.
Example of use:
<DL>
<DT>Term<DD>This is the definition of the first term.
<DT>Term<DD>This is the definition of the second term.
</DL>
If the DT term does not fit in the DT column (one third of the
display area), it may be extended across the page with the DD
section moved to the next line, or it may be wrapped onto
successive lines of the left hand column.
Single occurrences of a <DT> tag without a subsequent <DD> tag are
allowed, and have the same significance as if the <DD> tag had been
present with no text.
The opening list tag must be <DL> and must be immediately followed
by the first term (<DT>).
The definition list type can take the COMPACT attribute, which
suggests that a compact rendering be used, because the list items
are small and/or the entire list is large.
Unless you provide the COMPACT attribute, the HTML user agent may
leave white space between successive DT, DD pairs. The COMPACT
attribute may also reduce the width of the left-hand (DT) column.
If using the COMPACT attribute, the opening list tag must be <DL
COMPACT>, which must be immediately followed by the first <DT> tag:
<DL COMPACT>
<DT>Term<DD>This is the first definition in compact format.
<DT>Term<DD>This is the second definition in compact format.
</DL>
10.6.2 Directory List
<DIR> ... </DIR> Level 0
A Directory List element is used to present a list of items
containing up to 20 characters each. Items in a directory list may
be arranged in columns, typically 24 characters wide. If the HTML
user agent can optimize the column width as function of the widths
of individual elements, so much the better.
A directory list must begin with the <DIR> tag which is immediately
followed by a <LI> (list item) tag:
<DIR>
<LI>A-H<LI>I-M
<LI>M-R<LI>S-Z
</DIR>
10.6.3 Menu List
<MENU> ... </MENU> Level 0
A menu list is a list of items with typically one line per item.
The menu list style is more compact than the style of an unordered
list.
A menu list must begin with a <MENU> tag which is immediately
followed by a <LI> (list item) tag:
<MENU>
<LI>First item in the list.
<LI>Second item in the list.
<LI>Third item in the list.
</MENU>
10.6.4 Ordered List
<OL> ... </OL> Level 0
The Ordered List element is used to present a numbered list of
items, sorted by sequence or order of importance.
An ordered list must begin with the <OL> tag which is immediately
followed by a <LI> (list item) tag:
<OL>
<LI>Click the Web button to open the Open the URL window.
<LI>Enter the URL number in the text field of the Open URL
window. The Web document you specified is displayed.
<LI>Click highlighted text to move from one link to another.
</OL>
The Ordered List element can take the COMPACT attribute, which
suggests that a compact rendering be used.
10.6.5 Unordered List
<UL> ... </UL> Level 0
The Unordered List element is used to present a list of items which
is typically separated by white space and/or marked by bullets.
An unordered list must begin with the <UL> tag which is immediately
followed by a <LI> (list item) tag:
<UL>
<LI>First list item
<LI>Second list item
<LI>Third list item
</UL>
11. Form-based Input Elements
Forms are created by placing input fields within paragraphs,
preformatted/literal text, and lists. This gives considerable
flexibility in designing the layout of forms.
The following elements are used to create forms:
FORM
A form within a document.
INPUT
One input field.
OPTION
One option within a Select element.
SELECT
A selection from a finite set of options.
TEXTAREA
A multi-line input field.
Each variable field is defined by an Input, Textarea, or Option
element and must have an NAME attribute to identify its value in
the data returned when the form is submitted.
Example of use (a questionnaire form):
<H1>Sample Questionnaire</H1>
<P>Please fill out this questionnaire:
<FORM METHOD="POST" ACTION="http://www.w3.org/sample">
<P>Your name: <INPUT NAME="name" size="48">
<P>Male <INPUT NAME="gender" TYPE=RADIO VALUE="male">
<P>Female <INPUT NAME="gender" TYPE=RADIO VALUE="female">
<P>Number in family: <INPUT NAME="family" TYPE=text>
<P>Cities in which you maintain a residence:
<UL>
<LI>Kent <INPUT NAME="city" TYPE=checkbox VALUE="kent">
<LI>Miami <INPUT NAME="city" TYPE=checkbox VALUE="miami">
<LI>Other <TEXTAREA NAME="other" cols=48 rows=4></textarea>
</UL>
Nickname: <INPUT NAME="nickname" SIZE="42">
<P>Thank you for responding to this questionnaire.
<P><INPUT TYPE=SUBMIT> <INPUT TYPE=RESET>
</FORM>
In the example above, the <P> and <UL> tags have been used to lay
out the text and input fields. The HTML user agent is responsible
for handling which field will currently get keyboard input.
Many platforms have existing conventions for forms, for example,
using Tab and Shift keys to move the keyboard focus forwards and
backwards between fields, and using the Enter key to submit the
form. In the example, the SUBMIT and RESET buttons are specified
explicitly with special purpose fields. The SUBMIT button is used
to e-mail the form or send its contents to the server as specified
by the ACTION attribute, while RESET resets the fields to their
initial values. When the form consists of a single text field, it
may be appropriate to leave such buttons out and rely on the Enter
key.
The Input element is used for a large variety of types of input
fields.
To let users enter more than one line of text, use the Textarea
element.
The radio button and checkbox types of input field can be used to
specify multiple choice forms in which every alternative is visible
as part of the form. An alternative is to use the Select element
which is typically rendered in a more compact fashion as a pull
down combo list.
11.1 Form
<FORM> ... </FORM> Level 2
The Form element is used to delimit a data input form. There can be
several forms in a single document, but the Form element can't be
nested.
The ACTION attribute is a URL specifying the location to which the
contents of the form is submitted to elicit a response. If the
ACTION attribute is missing, the URL of the document itself is
assumed. The way data is submitted varies with the access protocol
of the URL, and with the values of the METHOD and ENCTYPE
attributes.
In general:
o the METHOD attribute selects variations in the protocol.
o the ENCTYPE attribute specifies the format of the submitted
data in case the protocol does not impose a format itself.
The Level 2 specification defines and requires support for the HTTP
access protocol only.
When the ACTION attribute is set to an HTTP URL, the METHOD
attribute must be set to an HTTP method [3]. The default method is
GET, although for many applications the POST method is preferred.
With the POST method, the ENCTYPE attribute is a media type
specifying the format of the posted data; the default is
"application/x-www-form-urlencoded".
The submitted contents of the form logically consist of name/value
pairs. The names are usually equal to the NAME attributes of the
various interactive elements in the form.
Note: The names are not guaranteed to be unique keys, nor
are the names of form elements required to be distinct. The
values encode the user's input to the corresponding
interactive elements. Fields with null values may be omitted
from the returned list of name/value pairs, whereas those
with non-null values should be included (even if the value
was not altered by the user). In particular, unselected
radio buttons and checkboxes should be excluded from the
contents list.
11.2 Input
<INPUT> Level 2
The Input element represents a field whose contents may be edited
by the user.
Attributes of the Input element:
ALIGN
Vertical alignment of the image. For use only with TYPE=IMAGE.
The possible values are exactly the same as for the ALIGN
attribute of the image element.
CHECKED
Indicates that a checkbox or radio button is selected.
Unselected checkboxes and radio buttons do not return name/value
pairs when the form is submitted.
MAXLENGTH
Indicates the maximum number of characters that can be entered
into a text field. This can be greater than specified by the
SIZE attribute, in which case the field will scroll
appropriately. The default number of characters is unlimited.
NAME
Symbolic name used when transferring the form's contents. The
NAME attribute is required for most input types and is normally
used to provide a unique identifier for a field, or for a
logically related group of fields.
SIZE
Specifies the size or precision of the field according to its
type. For example, to specify a field with a visible width of 24
characters:
INPUT TYPE=text SIZE="24"
SRC
A URL or URN specifying an image. For use only with TYPE=IMAGE.
TYPE
Defines the type of data the field accepts. Defaults to free
text. Several types of fields can be defined with the type
attribute:
CHECKBOX
Used for simple Boolean attributes, or for attributes that
can take multiple values at the same time. The latter is
represented by a number of checkbox fields each of which has
the same name. Each selected checkbox generates a separate
name/value pair in the submitted data, even if this results
in duplicate names. The default value for checkboxes is "on".
HIDDEN
No field is presented to the user, but the content of the
field is sent with the submitted form. This value may be used
to transmit state information about client/server interaction.
IMAGE
An image field upon which you can click with a pointing
device, causing the form to be immediately submitted. The
coordinates of the selected point are measured in pixel units
from the upper-left corner of the image, and are returned
(along with the other contents of the form) in two name/value
pairs. The x-coordinate is submitted under the name of the
field with ".x" appended, and the y-coordinate is submitted
under the name of the field with ".y" appended. Any VALUE
attribute is ignored. The image itself is specified by the
SRC attribute, exactly as for the Image element.
Note: In a future version of the HTML specification, the
IMAGE functionality may be folded into an enhanced SUBMIT
field.
PASSWORD
The same as the TEXT attribute, except that text is not
displayed as it is entered.
RADIO
Used for attributes that accept a single value from a set of
alternatives. Each radio button field in the group should be
given the same name. Only the selected radio button in the
group generates a name/value pair in the submitted data.
Radio buttons require an explicit VALUE attribute.
RESET
A button that when pressed resets the form's fields to their
specified initial values. The label to be displayed on the
button may be specified just as for the SUBMIT button.
SUBMIT
A button that when pressed submits the form. You can use the
VALUE attribute to provide a non-editable label to be
displayed on the button. The default label is application-
specific. If a SUBMIT button is pressed in order to submit
the form, and that button has a NAME attribute specified,
then that button contributes a name/value pair to the
submitted data. Otherwise, a SUBMIT button makes no
contribution to the submitted data.
TEXT
Used for a single line text entry fields. Use in conjunction
with the SIZE and MAXLENGTH attributes. Use the Textarea
element for text fields which can accept multiple lines.
VALUE
The initial displayed value of the field, if it displays a
textual or numerical value; or the value to be returned when the
field is selected, if it displays a Boolean value. This
attribute is required for radio buttons.
11.3 Option
<OPTION> Level 2
The Option element can only occur within a Select element. It
represents one choice, and can take these attributes:
SELECTED
Indicates that this option is initially selected.
VALUE
When present indicates the value to be returned if this option
is chosen. The returned value defaults to the contents of the
Option element.
The contents of the Option element is presented to the user to
represent the option. It is used as a returned value if the VALUE
attribute is not present.
11.4 Select
<SELECT NAME=... > ... </SELECT> Level 2
The Select element allows the user to chose one of a set of
alternatives described by textual labels. Every alternative is
represented by the Option element. Attributes are:
MULTIPLE
The MULTIPLE attribute is needed when users are allowed to make
several selections, e.g. <SELECT MULTIPLE>.
NAME
Specifies the name that will submitted as a name/value pair.
SIZE
Specifies the number of visible items. If this is greater than
one, then the resulting form control will be a list.
The Select element is typically rendered as a pull down or pop-up
list. For example:
<SELECT NAME="flavor">
<OPTION>Vanilla
<OPTION>Strawberry
<OPTION>Rum and Raisin
<OPTION>Peach and Orange
</SELECT>
If no option is initially marked as selected, then the first item
listed is selected.
11.5 Text Area
<TEXTAREA> ... </TEXTAREA> Level 2
The Textarea element lets users enter more than one line of text.
For example:
<TEXTAREA NAME="address" ROWS=64 COLS=6>
HaL Computer Systems
1315 Dell Avenue
Campbell, California 95008
</TEXTAREA>
The text up to the end tag (</TEXTAREA>) is used to initialize the
field's value. This end tag is always required even if the field is
initially blank. When submitting a form, lines in a TEXTAREA should
be terminated using CRLF.
In a typical rendering, the ROWS and COLS attributes determine the
visible dimension of the field in characters. The field is rendered
in a fixed-width font. HTML user agents should allow text to
extend beyond these limits by scrolling as needed.
Note: In the initial design for forms, multi-line text
fields were supported by the Input element with TYPE=TEXT.
Unfortunately, this causes problems for fields with long
text values. SGML's default (Reference Quantity Set) limits
the length of attribute literals to only 240 characters. The
HTML 2.0 SGML declaration increases the limit to 1024
characters.
12. HTML Document Type Definitions
12.1 Deprecated and Recommended Sections
Optional "deprecated" and "recommended" sections are used in the
HTML DTD. Conformance with this specification is defined with these
sections disabled. In the liberal spirit of Section 3.3, user
agents reading HTML documents should accept syntax corresponding to
the specification with "deprecated" turned on. On the other hand,
applications generating HTML should, in the conservative spirit,
generate documents that conform to the specification with the
"recommended" sections turned on.
12.2 Sample SGML Open Entity Catalog for HTML
The SGML standard describes an "entity manager" as the portion or
component of an SGML system that maps SGML entities into the actual
storage model (e.g., the file system). The standard itself does
not define a particular mapping methodology or notation.
To assist the interoperability among various SGML tools and
systems, the SGML Open consortium has passed a technical resolution
that defines a format for an application-independent entity catalog
that maps external identifiers and/or entity names to file names.
Each entry in the catalog associates a storage object identifier
(such as a file name) with information about the external entity
that appears in the SGML document. In addition to entries that
associate public identifiers, a catalog entry can associate an
entity name with a storage object indentifier. For example, the
following are possible catalog entries:
PUBLIC "ISO 8879:1986//ENTITIES Added Latin 1//EN" "iso-lat1.gml"
PUBLIC "-//ACME DTD Writers//DTD General Report//EN" report.dtd
ENTITY "graph1" "graphics\graph1.cgm"
In particular, the following shows entries relevant to HTML.
-- catalog: SGML Open style entity catalog for HTML --
-- Ways to refer to Level 2: most general to most specific --
PUBLIC "-//IETF//DTD HTML//EN" html.dtd
PUBLIC "-//IETF//DTD HTML 2.0//EN" html.dtd
PUBLIC "-//IETF//DTD HTML Level 2//EN" html.dtd
PUBLIC "-//IETF//DTD HTML 2.0 Level 2//EN" html.dtd
-- Ways to refer to Level 1: most general to most specific --
PUBLIC "-//IETF//DTD HTML Level 1//EN" html-1.dtd
PUBLIC "-//IETF//DTD HTML 2.0 Level 1//EN" html-1.dtd
-- Ways to refer to Level 0: most general to most specific --
PUBLIC "-//IETF//DTD HTML Level 0//EN" html-0.dtd
PUBLIC "-//IETF//DTD HTML 2.0 Level 0//EN" html-0.dtd
-- ISO latin 1 entity set for HTML --
PUBLIC "ISO 8879-1986//ENTITIES Added Latin 1//EN//HTML"
ISOlat1.sgml
12.3 SGML Declaration for HTML
This is the SGML Declaration for HyperText Markup Language (HTML)
as used by the World Wide Web (WWW) application:
<!SGML "ISO 8879:1986"
--
SGML Declaration for HyperText Markup Language (HTML).
--
CHARSET
BASESET "ISO 646:1983//CHARSET
International Reference Version
(IRV)//ESC 2/5 4/0"
DESCSET 0 9 UNUSED
9 2 9
11 2 UNUSED
13 1 13
14 18 UNUSED
32 95 32
127 1 UNUSED
BASESET "ISO Registration Number 100//CHARSET
ECMA-94 Right Part of
Latin Alphabet Nr. 1//ESC 2/13 4/1"
DESCSET 128 32 UNUSED
160 96 32
CAPACITY SGMLREF
TOTALCAP 150000
GRPCAP 150000
SCOPE DOCUMENT
SYNTAX
SHUNCHAR CONTROLS 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 127
BASESET "ISO 646:1983//CHARSET
International Reference Version
(IRV)//ESC 2/5 4/0"
DESCSET 0 128 0
FUNCTION
RE 13
RS 10
SPACE 32
TAB SEPCHAR 9
NAMING LCNMSTRT ""
UCNMSTRT ""
LCNMCHAR ".-"
UCNMCHAR ".-"
NAMECASE GENERAL YES
ENTITY NO
DELIM GENERAL SGMLREF
SHORTREF SGMLREF
NAMES SGMLREF
QUANTITY SGMLREF
ATTSPLEN 2100
LITLEN 1024
NAMELEN 72 -- somewhat arbitrary;
taken from Internet line
length conventions --
PILEN 1024
TAGLEN 2100
GRPGTCNT 150
GRPCNT 64
FEATURES
MINIMIZE
DATATAG NO
OMITTAG YES
RANK NO
SHORTTAG YES
LINK
SIMPLE NO
IMPLICIT NO
EXPLICIT NO
OTHER
CONCUR NO
SUBDOC NO
FORMAL YES
APPINFO "SDA" -- conforming SGML Document Access
application --
>
12.4 HTML Level 0 DTD
This is the Document Type Definition for the HyperText Markup
Language as used by minimally conforming World Wide Web
applications (HTML Level 0 DTD). Note that it is defined in terms
of the Level 2 DTD.
<!-- html-0.dtd
Document Type Definition for the HyperText Markup Language
as used by minimally conforming World Wide Web applications
(HTML Level 0 DTD).
-->
<!ENTITY % HTML.Version
"-//IETF//DTD HTML 2.0 Level 0//EN"
-- public identifier for "minimal conformance" version --
-- Typical usage:
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML Level 0//EN">
<html>
...
</html>
--
>
<!-- Feature Test Entities -->
<!ENTITY % HTML.Highlighting "IGNORE">
<!ENTITY % HTML.Forms "IGNORE">
<!ENTITY % head.extra " ">
<!ENTITY % linkExtraAttributes " ">
<!ENTITY % html PUBLIC "-//IETF//DTD HTML 2.0//EN">
%html;
12.5 HTML Level 1 DTD
This is the Document Type Definition for the HyperText Markup
Language with Level 1 Extensions (HTML Level 1 DTD). Note that it
is defined in terms of the Level 2 DTD.
<!-- html-1.dtd
Document Type Definition for the HyperText Markup Language
with Level 1 Extensions (HTML Level 1 DTD).
-->
<!ENTITY % HTML.Version
"-//IETF//DTD HTML 2.0 Level 1//EN"
-- Typical usage:
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML Level 1//EN">
<html>
...
</html>
--
>
<!-- Feature Test Entities -->
<!ENTITY % HTML.Forms "IGNORE">
<!ENTITY % html PUBLIC "-//IETF//DTD HTML 2.0//EN">
%html;
12.6 HTML Level 2 DTD
This is the Document Type Definition for the HyperText Markup
Language (HTML DTD):
<!-- html.dtd
Document Type Definition for the HyperText Markup Language
(HTML DTD)
-->
<!ENTITY % HTML.Version
"-//IETF//DTD HTML 2.0//EN"
-- Typical usage:
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML//EN">
<html>
...
</html>
--
>
<!--============ Feature Test Entities =======================-->
<!ENTITY % HTML.Recommended "IGNORE"
-- Certain features of the language are necessary for
compatibility with widespread usage, but they may
compromise the structural integrity of a document.
This feature test entity enables a more prescriptive
document type definition that eliminates
those features.
-->
<![ %HTML.Recommended [
<!ENTITY % HTML.Deprecated "IGNORE">
]]>
<!ENTITY % HTML.Deprecated "INCLUDE"
-- Certain features of the language are necessary for
compatibility with earlier versions of the specification,
but they tend to be used an implemented inconsistently,
and their use is deprecated. This feature test entity
enables a document type definition that eliminates
these features.
-->
<!ENTITY % HTML.Highlighting "INCLUDE"
-- Use this feature test entity to validate that a
document uses no highlighting tags, which may be
ignored on minimal implementations.
-->
<!ENTITY % HTML.Forms "INCLUDE"
-- Use this feature test entity to validate that a document
contains no forms, which may not be supported in minimal
implementations
-->
<!--============== Imported Names ============================-->
<!ENTITY % Content-Type "CDATA"
-- meaning an internet media type
(aka MIME content type, as per RFC1521)
-->
<!ENTITY % HTTP-Method "NAME"
-- as per HTTP specification, in progress
-->
<!ENTITY % URI "CDATA"
-- The term URI means a CDATA attribute
whose value is a Uniform Resource Identifier,
as defined by "Universal Resource Identifiers"
by Tim Berners-Lee, aka RFC 1630
Note that CDATA attributes are limited by the LITLEN
capacity (1024 in the current version of html.decl),
so that URIs in HTML have a bounded length.
-->
<!--========= DTD "Macros" =====================-->
<!ENTITY % heading "H1|H2|H3|H4|H5|H6">
<!ENTITY % list " UL | OL | DIR | MENU " >
<!--======= Character mnemonic entities =================-->
<!ENTITY % ISOlat1 PUBLIC
"ISO 8879-1986//ENTITIES Added Latin 1//EN//HTML">
%ISOlat1;
<!ENTITY amp CDATA "&" -- ampersand -->
<!ENTITY gt CDATA ">" -- greater than -->
<!ENTITY lt CDATA "<" -- less than -->
<!ENTITY quot CDATA """ -- double quote -->
<!--====== SGML Document Access (SDA) Parameter Entities =====-->
<!-- HTML 2.0 contains SGML Document Access (SDA) fixed
attributes in support of easy transformation to the
International Committee for Accessible Document Design
(ICADD) DTD "-//EC-USA-CDA/ICADD//DTD ICADD22//EN".
ICADD applications are designed to support usable access to
structured information by print-impaired individuals through
Braille, large print and voice synthesis. For more
information on SDA & ICADD:
- ISO 12083:1993, Annex A.8, Facilities for Braille,
large print and computer voice
- ICADD ListServ
<ICADD%ASUACAD.BITNET@ARIZVM1.ccit.arizona.edu>
- Usenet news group bit.listserv.easi
- Recording for the Blind, +1 800 221 4792
-->
<!ENTITY % SDAFORM "SDAFORM CDATA #FIXED"
-- one to one mapping -->
<!ENTITY % SDARULE "SDARULE CDATA #FIXED"
-- context-sensitive mapping -->
<!ENTITY % SDAPREF "SDAPREF CDATA #FIXED"
-- generated text prefix -->
<!ENTITY % SDASUFF "SDASUFF CDATA #FIXED"
-- generated text suffix -->
<!ENTITY % SDASUSP "SDASUSP NAME #FIXED"
-- suspend transform process -->
<!--========== Text Markup =====================-->
<![ %HTML.Highlighting [
<!ENTITY % font " TT | B | I ">
<!ENTITY % phrase
"EM | STRONG | CODE | SAMP | KBD | VAR | CITE ">
<!ENTITY % text "#PCDATA | A | IMG | BR | %phrase | %font">
<!ELEMENT (%font;|%phrase) - - (%text)*>
<!ATTLIST ( TT | CODE | SAMP | KBD | VAR )
%SDAFORM; "Lit"
>
<!ATTLIST ( B | STRONG )
%SDAFORM; "B"
>
<!ATTLIST ( I | EM | CITE )
%SDAFORM; "It"
>
<!-- <TT> Typewriter text -->
<!-- <B> Bold text -->
<!-- <I> Italic text -->
<!-- <EM> Emphasized phrase -->
<!-- <STRONG> Strong emphais -->
<!-- <CODE> Source code phrase -->
<!-- <SAMP> Sample text or characters -->
<!-- <KBD> Keyboard phrase, e.g. user input -->
<!-- <VAR> Variable phrase or substituable -->
<!-- <CITE> Name or title of cited work -->
<!ENTITY % pre.content "#PCDATA | A | HR | BR | %font | %phrase">
]]>
<!ENTITY % text "#PCDATA | A | IMG | BR">
<!ELEMENT BR - O EMPTY>
<!ATTLIST BR
%SDAPREF; "&#RE;"
>
<!-- <BR> Line break -->
<!--========= Link Markup ======================-->
<![ %HTML.Recommended [
<!ENTITY % linkName "ID">
]]>
<!ENTITY % linkName "CDATA">
<!ENTITY % linkType "NAMES"
-- a list of these will be specified at a later date -->
<!ENTITY % linkExtraAttributes
"REL %linkType #IMPLIED
REV %linkType #IMPLIED
URN CDATA #IMPLIED
TITLE CDATA #IMPLIED
METHODS NAMES #IMPLIED
">
<![ %HTML.Recommended [
<!ENTITY % A.content "(%text)*"
-- <H1><a name="xxx">Heading</a></H1>
is preferred to
<a name="xxx"><H1>Heading</H1></a>
-->
]]>
<!ENTITY % A.content "(%heading|%text)*">
<!ELEMENT A - - %A.content -(A)>
<!ATTLIST A
HREF %URI #IMPLIED
NAME %linkName #IMPLIED
%linkExtraAttributes;
%SDAPREF; "<Anchor: #AttList>"
>
<!-- <A> Anchor; source/destination of link -->
<!-- <A NAME="..."> Name of this anchor -->
<!-- <A HREF="..."> Address of link destination -->
<!-- <A URN="..."> Permanent address of destination -->
<!-- <A REL=...> Relationship to destination -->
<!-- <A REV=...> Relationship of destination to this -->
<!-- <A TITLE="..."> Title of destination (advisory) -->
<!-- <A METHODS="..."> Operations on destination (advisory) -->
<!--========== Images ==========================-->
<!ELEMENT IMG - O EMPTY>
<!ATTLIST IMG
SRC %URI; #REQUIRED
ALT CDATA #IMPLIED
ALIGN (top|middle|bottom) #IMPLIED
ISMAP (ISMAP) #IMPLIED
%SDAPREF; "<Fig><?SDATrans Img: #AttList>#AttVal(Alt)</Fig>"
>
<!-- <IMG> Image; icon, glyph or illustration -->
<!-- <IMG SRC="..."> Address of image object -->
<!-- <IMG ALT="..."> Textual alternative -->
<!-- <IMG ALIGN=...> Position relative to text -->
<!-- <IMG ISMAP> Each pixel can be a link -->
<!--========== Paragraphs=======================-->
<!ELEMENT P - O (%text)*>
<!ATTLIST P
%SDAFORM; "Para"
>
<!-- <P> Paragraph -->
<!--========== Headings, Titles, Sections ===============-->
<!ELEMENT HR - O EMPTY>
<!ATTLIST HR
%SDAPREF; "&#RE;&#RE;"
>
<!-- <HR> Horizontal rule -->
<!ELEMENT ( %heading ) - - (%text;)*>
<!ATTLIST H1
%SDAFORM; "H1"
>
<!ATTLIST H2
%SDAFORM; "H2"
>
<!ATTLIST H3
%SDAFORM; "H3"
>
<!ATTLIST H4
%SDAFORM; "H4"
>
<!ATTLIST H5
%SDAFORM; "H5"
>
<!ATTLIST H6
%SDAFORM; "H6"
>
<!-- <H1> Heading, level 1 -->
<!-- <H2> Heading, level 2 -->
<!-- <H3> Heading, level 3 -->
<!-- <H4> Heading, level 4 -->
<!-- <H5> Heading, level 5 -->
<!-- <H6> Heading, level 6 -->
<!--========== Text Flows ======================-->
<![ %HTML.Forms [
<!ENTITY % block.forms "BLOCKQUOTE | FORM | ISINDEX">
]]>
<!ENTITY % block.forms "BLOCKQUOTE">
<![ %HTML.Deprecated [
<!ENTITY % preformatted "PRE | XMP | LISTING">
]]>
<!ENTITY % preformatted "PRE">
<!ENTITY % block "P | %list | DL
| %preformatted
| %block.forms">
<!ENTITY % flow "(%text|%block)*">
<!ENTITY % pre.content "#PCDATA | A | HR | BR">
<!ELEMENT PRE - - (%pre.content)*>
<!ATTLIST PRE
WIDTH NUMBER #implied
%SDAFORM; "Lit"
>
<!-- <PRE> Preformatted text -->
<!-- <PRE WIDTH=...> Maximum characters per line -->
<![ %HTML.Deprecated [
<!ENTITY % literal "CDATA"
-- historical, non-conforming parsing mode where
the only markup signal is the end tag in full
-->
<!ELEMENT (XMP|LISTING) - - %literal>
<!ATTLIST XMP
%SDAFORM; "Lit"
%SDAPREF; "Example:&#RE;"
>
<!ATTLIST LISTING
%SDAFORM; "Lit"
%SDAPREF; "Listing:&#RE;"
>
<!-- <XMP> Example section -->
<!-- <LISTING> Computer listing -->
<!ELEMENT PLAINTEXT - O %literal>
<!-- <PLAINTEXT> Plain text passage -->
<!ATTLIST PLAINTEXT
%SDAFORM; "Lit"
>
]]>
<!--========== Lists ==================-->
<!ELEMENT DL - - (DT | DD)+>
<!ATTLIST DL
COMPACT (COMPACT) #IMPLIED
%SDAFORM; "List"
%SDAPREF; "Definition List:"
>
<!ELEMENT DT - O (%text)*>
<!ATTLIST DT
%SDAFORM; "Term"
>
<!ELEMENT DD - O %flow>
<!ATTLIST DD
%SDAFORM; "LItem"
>
<!-- <DL> Definition list, or glossary -->
<!-- <DL COMPACT> Compact style list -->
<!-- <DT> Term in definition list -->
<!-- <DD> Definition of term -->
<!ELEMENT (OL|UL) - - (LI)+>
<!ATTLIST OL
COMPACT (COMPACT) #IMPLIED
%SDAFORM; "List"
>
<!ATTLIST UL
COMPACT (COMPACT) #IMPLIED
%SDAFORM; "List"
>
<!-- <UL> Unordered list -->
<!-- <UL COMPACT> Compact list style -->
<!-- <OL> Ordered, or numbered list -->
<!-- <OL COMPACT> Compact list style -->
<!ELEMENT (DIR|MENU) - - (LI)+ -(%block)>
<!ATTLIST DIR
COMPACT (COMPACT) #IMPLIED
%SDAFORM; "List"
%SDAPREF; "<LHead>Directory</LHead>"
>
<!ATTLIST MENU
COMPACT (COMPACT) #IMPLIED
%SDAFORM; "List"
%SDAPREF; "<LHead>Menu</LHead>"
>
<!-- <DIR> Directory list -->
<!-- <DIR COMPACT> Compact list style -->
<!-- <MENU> Menu list -->
<!-- <MENU COMPACT> Compact list style -->
<!ELEMENT LI - O %flow>
<!ATTLIST LI
%SDAFORM; "LItem"
>
<!-- <LI> List item -->
<!--========== Document Body ===================-->
<![ %HTML.Recommended [
<!ENTITY % body.content "(%heading|%block|HR|ADDRESS|IMG)*"
-- <h1>Heading</h1>
<p>Text ...
is preferred to
<h1>Heading</h1>
Text ...
-->
]]>
<!ENTITY % body.content "(%heading | %text | %block |
HR | ADDRESS)*">
<!ELEMENT BODY O O %body.content>
<!-- <BODY> Document body -->
<!ELEMENT BLOCKQUOTE - - %body.content>
<!ATTLIST BLOCKQUOTE
%SDAFORM; "BQ"
>
<!-- <BLOCKQUOTE> Quoted passage -->
<!ELEMENT ADDRESS - - (%text|P)*>
<!ATTLIST ADDRESS
%SDAFORM; "Lit"
%SDAPREF; "Address:&#RE;"
>
<!-- <ADDRESS> Address, signature, or byline -->
<!--======= Forms ====================-->
<![ %HTML.Forms [
<!ELEMENT FORM - - %body.content
-(FORM) +(INPUT|SELECT|TEXTAREA)>
<!ATTLIST FORM
ACTION %URI #IMPLIED
METHOD (%HTTP-Method) GET
ENCTYPE %Content-Type; "application/x-www-form-urlencoded"
%SDAPREF; "<Para>Form:</Para>"
%SDASUFF; "<Para>Form End.</Para>"
>
<!-- <FORM> Fill-out or data-entry form -->
<!-- <FORM ACTION="..."> Address for completed form -->
<!-- <FORM METHOD=...> Method of submitting form -->
<!-- <FORM ENCTYPE="..."> Representation of form data -->
<!ENTITY % InputType "(TEXT | PASSWORD | CHECKBOX |
RADIO | SUBMIT | RESET |
IMAGE | HIDDEN )">
<!ELEMENT INPUT - O EMPTY>
<!ATTLIST INPUT
TYPE %InputType TEXT
NAME CDATA #IMPLIED
VALUE CDATA #IMPLIED
SRC %URI #IMPLIED
CHECKED (CHECKED) #IMPLIED
SIZE CDATA #IMPLIED
MAXLENGTH NUMBER #IMPLIED
ALIGN (top|middle|bottom) #IMPLIED
%SDAPREF; "Input: "
>
<!-- <INPUT> Form input datum -->
<!-- <INPUT TYPE=...> Type of input interaction -->
<!-- <INPUT NAME=...> Name of form datum -->
<!-- <INPUT VALUE="..."> Default/initial/selected value -->
<!-- <INPUT SRC="..."> Address of image -->
<!-- <INPUT CHECKED> Initial state is "on" -->
<!-- <INPUT SIZE=...> Field size hint -->
<!-- <INPUT MAXLENGTH=...> Data length maximum -->
<!-- <INPUT ALIGN=...> Image alignment -->
<!ELEMENT SELECT - - (OPTION+) -(INPUT|SELECT|TEXTAREA)>
<!ATTLIST SELECT
NAME CDATA #REQUIRED
SIZE NUMBER #IMPLIED
MULTIPLE (MULTIPLE) #IMPLIED
%SDAFORM; "List"
%SDAPREF;
"<LHead>Select #AttVal(Multiple)</LHead>"
>
<!-- <SELECT> Selection of option(s) -->
<!-- <SELECT NAME=...> Name of form datum -->
<!-- <SELECT SIZE=...> Options displayed at a time -->
<!-- <SELECT MULTIPLE> Multiple selections allowed -->
<!ELEMENT OPTION - O (#PCDATA)*>
<!ATTLIST OPTION
SELECTED (SELECTED) #IMPLIED
VALUE CDATA #IMPLIED
%SDAFORM; "LItem"
%SDAPREF;
"Option: #AttVal(Value) #AttVal(Selected)"
>
<!-- <OPTION> A selection option -->
<!-- <OPTION SELECTED> Initial state -->
<!-- <OPTION VALUE="..."> Form datum value for this option-->
<!ELEMENT TEXTAREA - - (#PCDATA)* -(INPUT|SELECT|TEXTAREA)>
<!ATTLIST TEXTAREA
NAME CDATA #REQUIRED
ROWS NUMBER #REQUIRED
COLS NUMBER #REQUIRED
%SDAFORM; "Para"
%SDAPREF; "Input Text -- #AttVal(Name): "
>
<!-- <TEXTAREA> An area for text input -->
<!-- <TEXTAREA NAME=...> Name of form datum -->
<!-- <TEXTAREA ROWS=...> Height of area -->
<!-- <TEXTAREA COLS=...> Width of area -->
]]>
<!--======= Document Head ======================-->
<![ %HTML.Recommended [
<!ENTITY % head.extra "META* & LINK*">
]]>
<!ENTITY % head.extra "NEXTID? & META* & LINK*">
<!ENTITY % head.content "TITLE & ISINDEX? & BASE? &
(%head.extra)">
<!ELEMENT HEAD O O (%head.content)>
<!-- <HEAD> Document head -->
<!ELEMENT TITLE - - (#PCDATA)*>
<!ATTLIST TITLE
%SDAFORM; "Ti"
>
<!-- <TITLE> Title of document -->
<!ELEMENT LINK - O EMPTY>
<!ATTLIST LINK
HREF %URI #REQUIRED
%linkExtraAttributes;
%SDAPREF; "Linked to : #AttVal (TITLE) (URN) (HREF)>"
>
<!-- <LINK> Link from this document -->
<!-- <LINK HREF="..."> Address of link destination -->
<!-- <LINK URN="..."> Lasting name of destination -->
<!-- <LINK REL=...> Relationship to destination -->
<!-- <LINK REV=...> Relationship of destination to this -->
<!-- <LINK TITLE="..."> Title of destination (advisory) -->
<!-- <LINK METHODS="..."> Operations allowed (advisory) -->
<!ELEMENT ISINDEX - O EMPTY>
<!ATTLIST ISINDEX
%SDAPREF;
"<Para>[Document is indexed/searchable.]</Para>"
>
<!-- <ISINDEX> Document is a searchable index -->
<!ELEMENT BASE - O EMPTY>
<!ATTLIST BASE
HREF %URI; #REQUIRED
>
<!-- <BASE> Base context document -->
<!-- <BASE HREF="..."> Address for this document -->
<!ELEMENT NEXTID - O EMPTY>
<!ATTLIST NEXTID
N %linkName #REQUIRED
>
<!-- <NEXTID> Next ID to use for link name -->
<!-- <NEXTID N=...> Next ID to use for link name -->
<!ELEMENT META - O EMPTY>
<!ATTLIST META
HTTP-EQUIV NAME #IMPLIED
NAME NAME #IMPLIED
CONTENT CDATA #REQUIRED
>
<!-- <META> Generic Metainformation -->
<!-- <META HTTP-EQUIV=...> HTTP response header name -->
<!-- <META NAME=...> Metainformation name -->
<!-- <META CONTENT="..."> Associated information -->
<!--======= Document Structure =================-->
<![ %HTML.Deprecated [
<!ENTITY % html.content "HEAD, BODY, PLAINTEXT?">
]]>
<!ENTITY % html.content "HEAD, BODY">
<!ELEMENT HTML O O (%html.content)>
<!ENTITY % version.attr "VERSION CDATA #FIXED '%HTML.Version;'">
<!ATTLIST HTML
%version.attr;
%SDAFORM; "Book"
>
<!-- <HTML> HTML Document -->
13. Character Entity Sets
The following entity names are used in HTML, always prefixed by
ampersand (&) and followed by a semicolon as shown. They represent
particular graphic characters which have special meanings in places
in the markup, or may not be part of the character set available to
the writer.
13.1 Numeric and Special Graphic Entity Set
The following table lists each of the supported characters
specified in the Numeric and Special Graphic entity set, along with
its name, syntax for use, and description. This list is derived
from ISO Standard 8879:1986//ENTITIES Numeric and Special
Graphic//EN. However, HTML does not provide support for the entire
entity set -- only the entities listed below are supported.
GLYPH NAME SYNTAX DESCRIPTION
< lt < Less than sign
> gt > Greater than sign
& amp & Ampersand
" quot " Double quote sign
13.2 ISO Latin 1 Character Entity Set
The following table lists each of the characters specified in the
Added Latin 1 entity set, along with its name, syntax for use, and
description. This list is derived from ISO Standard
8879:1986//ENTITIES Added Latin 1//EN. HTML supports the entire
entity set.
NAME SYNTAX DESCRIPTION
Aacute Á Capital A, acute accent
Agrave À Capital A, grave accent
Acirc  Capital A, circumflex accent
Atilde à Capital A, tilde
Aring Å Capital A, ring
Auml Ä Capital A, dieresis or umlaut mark
AElig Æ Capital AE dipthong (ligature)
Ccedil Ç Capital C, cedilla
Eacute É Capital E, acute accent
Egrave È Capital E, grave accent
Ecirc Ê Capital E, circumflex accent
Euml Ë Capital E, dieresis or umlaut mark
Iacute Í Capital I, acute accent
Igrave Ì Capital I, grave accent
Icirc Î Capital I, circumflex accent
Iuml Ï Capital I, dieresis or umlaut mark
ETH Ð Capital Eth, Icelandic
Ntilde Ñ Capital N, tilde
Oacute Ó Capital O, acute accent
Ograve Ò Capital O, grave accent
Ocirc Ô Capital O, circumflex accent
Otilde Õ Capital O, tilde
Ouml Ö Capital O, dieresis or umlaut mark
Oslash Ø Capital O, slash
Uacute Ú Capital U, acute accent
Ugrave Ù Capital U, grave accent
Ucirc Û Capital U, circumflex accent
Uuml Ü Capital U, dieresis or umlaut mark
Yacute Ý Capital Y, acute accent
THORN Þ Capital THORN, Icelandic
szlig ß Small sharp s, German (sz ligature)
aacute á Small a, acute accent
agrave à Small a, grave accent
acirc â Small a, circumflex accent
atilde ã Small a, tilde
aring å Small a, ring
auml ä Small a, dieresis or umlaut mark
aelig æ Small ae dipthong (ligature)
ccedil ç Small c, cedilla
eacute é Small e, acute accent
egrave è Small e, grave accent
ecirc ê Small e, circumflex accent
euml ë Small e, dieresis or umlaut mark
iacute í Small i, acute accent
igrave ì Small i, grave accent
icirc î Small i, circumflex accent
iuml ï Small i, dieresis or umlaut mark
eth ð Small eth, Icelandic
ntilde ñ Small n, tilde
oacute ó Small o, acute accent
ograve ò Small o, grave accent
ocirc ô Small o, circumflex accent
otilde õ Small o, tilde
ouml ö Small o, dieresis or umlaut mark
oslash ø Small o, slash
uacute ú Small u, acute accent
ugrave ù Small u, grave accent
ucirc û Small u, circumflex accent
uuml ü Small u, dieresis or umlaut mark
yacute ý Small y, acute accent
thorn þ Small thorn, Icelandic
yuml ÿ Small y, dieresis or umlaut mark
14. Security Considerations
Anchors, embedded images, and all other elements which contain URIs
as parameters may cause the URI to be dereferenced in response to
user input. In this case, the security considerations of the URI
specification apply.
Documents may be constructed whose visible contents mislead the
reader to follow a link to unsuitable or offensive material.
15. References
[1] T. Berners-Lee. "Universal Resource Identifiers in WWW: A
Unifying Syntax for the Expression of Names and Addresses of
Objects on the Network as used in the World-Wide Web."
RFC 1630, CERN, June 1994.
[2] T. Berners-Lee, L. Masinter, and M. McCahill. "Uniform Resource
Locators (URL)." RFC 1738, CERN, Xerox PARC, University of
Minnesota, October 1994.
[3] T. Berners-Lee, R. T. Fielding, and H. Frystyk Nielsen.
"Hypertext Transfer Protocol -- HTTP/1.0." Work in Progress
(draft-ietf-http-v10-spec-00.ps), MIT, UC Irvine, CERN,
March 1995.
[4] N. Borenstein and N. Freed. "MIME (Multipurpose Internet Mail
Extensions) Part One: Mechanisms for Specifying and Describing
the Format of Internet Message Bodies." RFC 1521, Bellcore,
Innosoft, September 1993.
[5] R. T. Fielding. "Relative Uniform Resource Locators." Work in
Progress (draft-ietf-uri-relative-url-06.txt), UC Irvine,
March 1995.
[6] C. F. Goldfarb. "The SGML Handbook." Y. Rubinsky, Ed., Oxford
University Press, 1990.
[7] J. Postel. "Media Type Registration Procedure." RFC 1590,
USC/ISI, March 1994.
[8] J. Reynolds and J. Postel. "Assigned Numbers." STD 2, RFC 1700,
USC/ISI, October 1994.
[9] SoftQuad. "The SGML Primer." 3rd ed., SoftQuad Inc., 1991.
[10] US-ASCII. Coded Character Set - 7-Bit American Standard Code
for Information Interchange. Standard ANSI X3.4-1986, ANSI,
1986.
[11] ISO 8859. International Standard -- Information Processing --
8-bit Single-Byte Coded Graphic Character Sets -- Part 1: Latin
Alphabet No. 1, ISO 8859-1:1987. Part 2: Latin alphabet No. 2,
ISO 8859-2, 1987. Part 3: Latin alphabet No. 3, ISO 8859-3,
1988. Part 4: Latin alphabet No. 4, ISO 8859-4, 1988. Part 5:
Latin/Cyrillic alphabet, ISO 8859-5, 1988. Part 6: Latin/Arabic
alphabet, ISO 8859-6, 1987. Part 7: Latin/Greek alphabet, ISO
8859-7, 1987. Part 8: Latin/Hebrew alphabet, ISO 8859-8, 1988.
Part 9: Latin alphabet No. 5, ISO 8859-9, 1990.
[12] ISO 8879. Information Processing -- Text and Office Systems --
Standard Generalized Markup Language (SGML), 1986.
16. Acknowledgments
The HTML document type was designed by Tim Berners-Lee at CERN as
part of the 1990 World Wide Web project. In 1992, Dan Connolly
wrote the HTML Document Type Definition (DTD) and a brief HTML
specification.
Since 1993, a wide variety of Internet participants have
contributed to the evolution of HTML, which has included the
addition of in-line images introduced by the NCSA Mosaic software
for WWW. Dave Raggett played an important role in deriving the
FORMS material from the HTML+ specification.
Dan Connolly and Karen Olson Muldrow rewrote the HTML Specification
in 1994. The document was then edited by the HTML working group as
a whole, with updates being made by Eric Schieler, Mike Knezovich,
and Eric W. Sink at Spyglass, Inc. Finally, Roy Fielding
restructured the entire draft into its current form.
Special thanks to the many people who have contributed to this
specification:
Terry Allen Marc Andreessen
Tim Berners-Lee Paul Burchard
James Clark Daniel W. Connolly
Roy T. Fielding Peter Flynn
Jay Glicksman Paul Grosso
Eduardo Gutentag Bill Hefley
Chung-Jen Ho Mike Knezovich
Tom Magliery Murray Maloney
Larry Masinter Karen Olson Muldrow
Bill Perry Dave Raggett
E. Corprew Reed Yuri Rubinsky
Eric Schieler James L. Seidman
Eric W. Sink Stuart Weibel
Chris Wilson Francois Yergeau
17. Authors' Addresses
Tim Berners-Lee
Director, W3 Consortium
MIT Laboratory for Computer Science
545 Technology Square
Cambridge, MA 02139, U.S.A.
Tel: +1 (617) 253 9670
Fax: +1 (617) 258 8682
Email: timbl@w3.org
Daniel W. Connolly
Research Technical Staff, W3 Consortium
MIT Laboratory for Computer Science
545 Technology Square
Cambridge, MA 02139, U.S.A.
Fax: +1 (617) 258 8682
Email: connolly@w3.org
URL: http://www.w3.org/hypertext/WWW/People/Connolly/
Appendices
These appendices are provided for informational reasons only -- they
do not form a part of the HTML specification.
A. Obsolete Features
This section describes elements that are no longer part of HTML.
User agent implementors should implement these obsolete elements for
compatibility with previous versions of the HTML specification.
A.1 Comment Element
The Comment element is used to delimit unneeded text and comments.
The Comment element has been introduced in some HTML applications
but should be replaced by the SGML comment feature in new HTML
user agents (see Section 2.2.5).
A.2 Highlighted Phrase Element
<HP>
The Highlighted Phrase element should be ignored if not
implemented. This element has been replaced by more meaningful
elements (see Section 8).
Example of use:
<HP1>first highlighted phrase</HP1>non-highlighted
text<HP2>second highlighted phrase</HP2> etc.
A.3 Plain Text Element
<PLAINTEXT>
The Plain Text element is used to terminates the HTML entity and to
indicate that what follows is not SGML which does not require
parsing. Instead, an old HTTP convention specified that what
followed was an ASCII (MIME "text/plain") body. Its presence is an
optimization. There is no closing tag.
Example of use:
<PLAINTEXT>
0001 This is line one of a long listing
0002 file from <ANY@HOST.INC.COM> which is sent
A.4 Example and Listing Elements
<XMP> ... </XMP> and <LISTING> ... </LISTING>
The Example and Listing elements have been replaced by the
Preformatted Text element (Section 10.2).
These styles allow text of fixed-width characters to be embedded
absolutely as is into the document. The syntax is:
<LISTING> ... </LISTING>
or
<XMP> ... </XMP>
The text between these tags is typically rendered in a monospaced
font so that any formatting done by character spacing on successive
lines will be maintained.
Between the opening and closing tags:
o The text may contain any ISO Latin-1 printable characters,
expect for the end tag opener. The Example and Listing elements
have historically used specifications which do not conform to
SGML. Specifically, the text may contain ISO Latin printable
characters, including the tag opener, as long it they does not
contain the closing tag in full.
o SGML does not support this form. HTML user agents may vary on
how they interpret other tags within Example and Listing
elements.
o Line boundaries within the text are rendered as a move to the
beginning of the next line, except for one immediately
following a start tag or immediately preceding an end tag.
o The horizontal tab character must be interpreted as the
smallest positive nonzero number of spaces which will leave the
number of characters so far on the line as a multiple of 8. Its
use is not recommended.
The Listing element is rendered so that at least 132 characters fit
on a line. The Example element is rendered to that at least 80
characters fit on a line but is otherwise identical to the Listing
element.
B. Proposed Features
This section describes proposed HTML elements and entities that are
not currently supported under HTML Levels 0, 1, or 2, but may be
supported in the future.
B.1 Additional Character Entities
To indicate special characters, HTML uses entity or numeric
representations. Additional character presentations are proposed:
CHARACTER REPRESENTATION
Non-breaking space
Soft-hyphen ­
Registered ®
Copyright ©
B.2 Defining Instance Element
<DFN> ... </DFN>
The Defining Instance element indicates the defining instance of a
term. The typical rendering is bold or bold italic. This element is
not widely supported.
B.3 Strike Element
<STRIKE> ... </STRIKE>
The Strike element is proposed to indicate strikethrough, a font
style in which a horizontal line appears through characters. This
element is not widely supported.
B.4 Underline Element
<U> ... </U>
The Underline element is proposed to indicate that the text should
be rendered as underlined. This proposed tag is not supported by
all HTML user agents.
Example of use:
The text <U>shown here</U> is rendered in the document as
underlined.