HTML5 doctype not 'cascading' to every page in website?

Without showing the structure of my website, can anyone guess why t开发者_如何学JAVAhe HTML5 doctype is not changing, for example:

www.mysite.com/x (ok- html5)
www.mysite.com/x/a (ok- html5)
www.mysite.com/y (ok- html5)
www.mysite.com/y/a (xhtml doctype)

More info: I'm using Kentico CMS.

I suspect you have multiple master pages and some URLs use the HTML5 doctype masterpage and other URLs use a different masterpage.

Try searching your files for those alternate doctype values in your Kentico CMS files and see what shows up.