Language Tagging in HTML

When specifying the language of text or links which does not match the language of the page, the language should be specified using lang="xx" xml:lang="xx" where you would replace "xx".
Here is a complete list of language tags used on the Invest in Canada website.
A few examples:
<span lang="fr" xml:lang="fr">(anglais seulement)</span>
<span lang="en" xml:lang="en">(French only)</span>
<a href="http://www.investottawa.com" lang="en" xml:lang="en">Invest in Ottawa</a>