I am trying to develop CSS selectors to use with Selenium. In particular I want to use the pseudo-class :contains(). Although the W3 has a draft of CSS3 with :contains() i
jQuery's selector engine also implements the :contains() pseudo-class. It is to my knowledge that jQuery and Selenium implement it the same way.
I'm not sure how you would be able to test it on sites that don't make use of jQuery, but on sites that do, it's just a matter of firing up your browser's JavaScript console, and running jQuery selectors in the console.
Here's an example with viewing this very Stack Overflow question on Chrome's JavaScript console (you may get different results depending on whether you're logged in or not):
> $("#mainbar div[id]:contains('selector')").get() /* DOM objects with .get() */
[…, …, …, …]