I have a website that a client requires to be XHTML valid. They check it using the W3C validator.

I want to add my own namespace and attributes so I can do things like this:

<div my:userid="123"> ... </div>

From what I understand, defining custom namespaces is perfectly valid XHTML, as long as I do this:

<html xmlns="http://www.w3.org/1999/xhtml" xmlns:my="http://www.example.com/my">

However, my XHTML fails validation. The problem appears to be that the validator does not actually go out and check my custom DTD document for my custom namespace, it only checks the XHTML against known DTD's. Anyone able to shed any light on how I can solve this problem?

validation xhtml namespaces
Edit
Report