I decided to use pure XML+CSS instead of (X)HTML for my webpage. I use and with no problems. However I can't specify webpage's title.
Document looks like this:
<?xml version="1.0" ?>
<?xml-stylesheet type="text/css" href="style.css"?>
<html:html xmlns:html="http://www.w3.org/1999/xhtml">
<html:head>
<html:title>FooBar</html:title>
</html:head>
<site>
<header>foo</header>
<article>
<title>foo</title>
<p>foo bar <html:a href="#">foobar</html:a></p>
</article>
</site>
</html:html>
But it doesn't work.
Update: it works on Chrome and Internet Explorer. Doesn't work on Firefox.