“v5.master” is a simple HTML5 master page designed for SharePoint 2010. It makes good use of the amazing new features of both HTML5 and CSS3, including CSS3 media queries. The master page is extremely simplistic in nature, and is truly meant to serve as a framework for building your own SharePoint 2010 customizations.

Here comes some good news for SharePoint and HTML 5. If you want to build your masterpage for HTML 5, you can: http://kyleschaeffer.com/sharepoint/v5-responsive-html5-master-page/

Thank you, Kyle!