sorry,

accepted:-)

Of course if the documents that you are serving are at all interesting
they will of course! have mathematics in them, which means that they will
have xhtml+mathml. Now the Math rendering is only enabled in the XML side
of mozilla (not unreasonably as XHTML and MathML are both XML languages)
so in that case the option of producing a valid XML document but sending
it as text/html to the browser's legacy tag soup parser is _not_
available.

David