Is there any problem with using HTML5's "data-*" attributes for older browsers?

I want to associate some custom data with some HTML nodes. I was going to use the new HTML5 style 'data-*' attributes. e.g.: <tr class="foo" data-typeid="7">…, and then I was going to select this HTML node and show/hide it etc. by reading the value with $(node).attr("data-typeid").

However this web page needs to work with older browsers aswell. I'm not using the data-* attribute as a special attribute, but I'd like to know if older browsers will ignore, wipe, or make inaccessible this attribute since it's not valid HTML4.

There isn't really, they're not 100% correct/valid usage in HTML4 of course....but they don't cause problems either, so they're still a great way to solve the "I need an attribute for this" problem.

If it helps, I've used these while supporting IE6 and have had zero issues thus far, and I can't recall a single SO question reporting any either.

Internet Explorer and Microsoft has added several custom attributes that are not valid HTML4. Browsers don't check the element attributes against a specification, you can name an attribute roryscoolinfo="hello" if you like (though you shouldn't).

The Dojo Toolkit adds its custom dojo* attributes.

It's fine to use data- today, with a HTML5 doctype.