I included "Mozilla" in my list, and intended for that to cover Firefox and any other browser derived from the Mozilla codebase. Certainly any version of Firefox will do - even versions from back when it was called "Phoenix".
Check your HTTP headers:
perl -MLWP::UserAgent -e'print LWP::UserAgent->new->get("http://localh
I'm guessing you'll see Content-Type: text/html. As I said, my example is XHTML, and assumes that the page is served with the correct XHTML media type Content-Type: application/xhtml+xml. Adding a <meta> tag to the document will not make any difference.