www.w3.org served as text/html and application/xhtml+xml

Hi!

Why www.w3.org is XHTML 1.0 Strict document served using text/html MIME
type? I found on this mailing list that there are some compatibility
issues. However is it possible to serve www.w3.org as application/xhtml+xml
and text/html at the same time? When request contains HTTP Accept header
with application/xhtml+xml, document may be served as XML in other cases as
text/html, as mentioned in
http://www.w3.org/TR/xhtml-media-types/#media-types.

Is there any known problem with browser that receive XHTML document written
in accordance with the HTML Compatibility Guidelines (
http://www.w3.org/TR/xhtml1/ # guidelines) and served as text/html?

Inzynier