higgo/h5bp-redux — pull request #1 by pankajparashar (2012-09-09 10:03:34+00:00)
Title: Changed doctype to DOCTYPE

In HTML, the DOCTYPE is case insensitive. The following DOCTYPES are all valid:

In XML serializations (i.e. XHTML) the DOCTYPE is not required, but if you use it, DOCTYPE should be uppercase:

See The XML serialization of HTML5, aka ‘XHTML5’:

Note that if you don’t uppercase DOCTYPE in an XHTML document, the XML parser will return a syntax error.

The second part can be written in lowercase (html), uppercase (HTML) or even mixed case (hTmL) — it will still work. However, to conform to the Polyglot Markup Guidelines for HTML-Compatible XHTML Documents, it should be written in lowercase.

Hence, as per W3C Polyglot markup guidelines, the recommended doctype should be -

More Information - http://goo.gl/Rboe5