You are using Frameset DTD , which does not allow the body. It is intended for use with framesets, which are used to display frames. Instead, you can use Strict:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en">
<head>
<title>Test</title>
</head>
<body>
</body>
</html>
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