From the Mozilla FAQ:

In reply to:

Why isn't my stylesheet applied?
Make sure the mime type for both source and stylesheet are set to a XML mimetype, namely text/xml or application/xml. The XSLT namespace is http://www.w3.org/1999/XSL/Transform. Mime type handling in Mozilla is strict, in contrast to IE. Write some cgi, and you'll love it.


Unless Hijack has changed... I believe it is correct.

Tom