Snib, I noticed your comment in reference to using XHTML 1.1 with the Validator. I take it you're aware that the Validator doesn't send HTTP_ACCEPT? If serving XHTML to the Validator, it is best to use a MIME header rewrite test such as that suggested by Richard Allsebrook as a modification to the code in this articlehttp://www.xml.com/pub/a/2003/03/19/dive-into-xml.html on O'Reilly's excellent XML.com - namely:

if ( isset($_SERVER["HTTP_ACCEPT"]) and stristr($_SERVER["HTTP_ACCEPT"],"application/xhtml+xml") ) {
 header("Content-type: application/xhtml+xml");
 }
 else {
 header("Content-type: text/html");
 }
}

This will send the correct MIME header (and incidentally trns Mozilla into an excellent XML debugging tool.

I just thought I'd mention it, in case you hadn't come across this before.

Dan