Couldn't this section just be removed?
As I understand it, it only describes the
recommended behaviour for browsers upon
encountering invalid documents. Any smart
browser implementor should be able to figure
this out on their own.
The presence of this section in the specification
is widely interpreted by users as offering carte blanche
to invent whatever new tags and attributes they feel like.
How about: "In the case of an unknown tag, the
results are undefined." That better reflects
the true situation -- some browsers are known to do
strange things with unknown tags, like making
the content blink or centering it.
Does the specification *really* need to say anything
about what to do with illegal documents?
--Joe English
joe@trystero.art.com