HTML and XML are structural foundations of every website or application. It is crucial that developers learn — and master — both.

Automatic language switching lets you create a multi-lingual website. Switching between multiple languages is done using special tags, plug-ins or an embedded code. The auto language switching plug-in ...

Google's John Mueller confirmed that they completely ignore the HTML lang attribute for determining the language and region of the page. John said this at the 55:54 mark into the video hangout ...