HTML5 <html> attributes xmlns, lang, xml:lang
I don't understand the HTML5 specifications for the lang and xml:lang attributes of the opening <html> tag. Scrolling up a bit, I understand that xmlns is a "talisman" (has no effect), but what about lang and xml:lang? Should they be used? If so, what should they be set to?
Everything I've seen and heard suggests that you should stick to
<!DOCTYPE html> <html> <head> <meta charset='UTF-8'>
(or whatever character set you actually want). If you want a language associated with the page you can use the "lang" attribute on the <html> tag.
Since HTML5 is not XML, really, I personally would find it weird to use any xml: namespace stuff.