Whilst the 4.4 release predominantly focussed on performance and optimisation, there were a number of other enhancements added to the release (as always the changelog is the best place to view changes). One of these, that should be of interest to skinners and those interested in accessibility standards & xhtml compliance, is support for skin level doctypes . Historically, if you wanted to target your skin/container for a particular version of html/xhtml, you had to manually edit the default.aspx page to alter the hardcoded DOCTYPE declaration. With 4.4, the declaration has been made dynamic, to allow users to declare particular doctypes with particular skins. To make use of this, you create a file with the same name as your skin except ending in doctype.xml (rather than ascx/htm/html) and it’ll be picked up during skin load. This xml file should contain a single node,SkinDocType, that contains a declaration of your desired doctype. To ensure that the parser reads the value correctly, you need to use a CDATA section to escape out the various < and & characters e.g. If I have a skin called mypage.asx that I intended to render as XHTML 1.0 strict, then I would create a file called mypage.doctype.xml which would contain the following: