Section 5.1 of the XHTML 1.0 Second Edition spec states:
XHTML Documents which follow the guidelines set forth in
Appendix C, "HTML Compatibility Guidelines" may be labeled with
the Internet Media Type "text/html" [RFC2854], as they are
compatible with most HTML browsers.
This is the only part of the XHTML spec which defines what documents may
be served as text/html (and is normative). However the entire of
Appendix C is *informative* and phrased in non-RFC 2119 language so, as
far as I can tell, doesn't actually make any requirements that need to
be followed.
--
David Dorward <http://dorward.me.uk/>
"Anybody remotely interesting is mad, in some way or another."
-- The Greatest Show in the Galaxy
