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

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


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

Answer

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.