Are you talking about the "Server Push" Netscape 1.1 implements using
Multipart content types? If so, the concept isn't that there's one
document with multiple <TITLE> and <BODY> tags, but that there are
multiple documents. I think it's better to go along the lines of
existing standards (MIME) rather than inventing new ones whenever
possible.
If you're not talking about "Server Push", then I'm curious about
what you are talking about that has the behavior you described.
It's impossible to keep track of what everyone's cooking up.
Kief