twbs/bootstrap — pull request #9217 by kevinSuttle (2013-08-08 03:41:29+00:00)
Title: Add <main> element

See:
http://www.w3.org/html/wg/drafts/html/master/grouping-content.html#the-main-element

http://www.filamentgroup.com/lab/the_main_element/

http://html5doctor.com/the-main-element/