xmlns appropriate in HTML5?
<!DOCTYPE html> <html xmlns="http://www.w3.org/1999/xhtml"> ... </html>
Also, which is preferred,
<!DOCTYPE html> or
The HTML5 drafts are partly rather complicated and abstract. But on the basis of somewhat vague statements in them as well as the http://validator.w3.org behavior (which can be expected to reflect the intentions of the authors of HTML5 drafts, the answers seem to be:
In XHTML syntax, the doctype string must be cased as in
According to HTML5 Reference,