HTML validation

Per http://www.w3.org/TR/html5/dom.html#the-lang-and-xml:lang-attributes, `xml:lang` should be omitted: "Authors must not use the lang attribute in the XML namespace on HTML elements in HTML documents."

Use HTML entity (`&amp;`) for `&` in `href` attribute.

I guarantee this is the most trivial pull request you will receive all week.