Gadgetopia

HTML 5 data- Attributes: HTML and XML begin to merge.

Simply, the specification for custom data attributes states that any attribute that starts with “data-” will be treated as a storage area for private data (private in the sense that the end user can’t see it - it doesn’t affect layout or presentation).

So, you could have:

<div data-firstname="Deane" data-lastname="Barker>

Of course, you can do this now. You’ll just validate in HTML 5.