HTML Question

I cannot validate this blank HTML page to XHTML 5.1

I cannot validate this blank page to XHTML 5.1.

<!DOCTYPE html>
<meta charset="utf-8" />
<title>XHTML 5.1 blank page</title>

<h1>Blank page</h1>
<p>Text here.</p>

All tags are well-closed and I specific the DOCTYPE, what I'm wrong?

Answer Source

You need requires that the attribute indicated should be used. xmlns And you should look this if you sse the 'lang' or 'xml:lang' attribute to denote the language of the document.