Discussion on DOCTYPE and SharePoint 2010 Pages
When you create new ASPX pages (without a master page) or HTML pages in SharePoint Designer, by default, those pages include a Document Type (DOCTYPE) definition, located in the header section at the top of the page. By default, the DOCTYPE is set to conform to the xhtml1-strict.dtd definition as published by the Worldwide Web Consortium (W3C):
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN""http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"><%@ Page Language="C#" %><html dir="ltr" xmlns="http://www.w3.org/1999/xhtml">
DOCTYPE General Definition
For those unfamiliar with DOCTYPES, the DOCTYPE definition defines the markup declarations, or structure, for page/s within a website and how those ...