title: VS2010/VS2012 default Doctypes and which to use to be future-proof
body: <p>I was wondering why VS2010 and VS2012 use different doctype declarations for masterpages and webforms.</p>
  
  <p>i.e. VS2010 uses the "XHTML 1.0 Strict" doctype for masterpages and the "XHTML 1.0 Transitional" doctype for webforms. </p>
  
  <p>VS2012 uses HTML5 "DOCTYPE html" for masterpages and adds the XHTML namespace (xmlns="http://www.w3.org/1999/xhtml") to the body tags of web forms.</p>
  
  <p>Is there any reason for this behaviour?</p>
  
  <p>I am trying to find out what doctype I should use for a relaunch of a website. I want to support older IE and FF versions too but I do not want to use the new HTML5 Tags/Attributes (at the moment,  but propably I will use them somewhen in the future).</p>
  
  <p>The website is developed in VS2010 with ASP.NET 4.0 but I will change to VS2012 with ASP.NET 4.5 as soon as possible. And this is my very problem which unsettles me. As mentioned the two versions use different doctype declarations and now I do not know what to do to be future-proof and tolerant of older browsers.</p>
  
  <p>thanks in advance for your answers</p>
  
  <p>PS: I do not want to use MIME types other than text/html</p>