Avoid the Deprecated <xml> Tag in HTML 5

The <xml> tag should be avoided because it has been deprecated. Any XML can be included by using an XML top element with an xmlns attribute and then transformed to HTML using a <xml-stylesheet> instruction.

Note that this <xml> tag, which should not be used, is not the same thing as the <xml> declaration which does still appear at the very beginning of documents using the current version of HTML code.