I don\'t understand the HTML5 specifications for the lang and xml:lang attributes of the opening tag. Scrolling up a bit, I understand that
x
Everything I've seen and heard suggests that you should stick to
(or whatever character set you actually want). If you want a language associated with the page you can use the "lang" attribute on the tag.
Since HTML5 is not XML, really, I personally would find it weird to use any xml:
namespace stuff.