Is there a GUI framework that uses HTML and CSS to build GUIs?

I mean, other than a browser, of course -- I'm talking about building native applications with HTML and CSS -- not web applications, but real nat开发者_StackOverflowive GUIs.

I wonder if such a thing exists?

And what do you think of such a beast? What would the pros/cons of such a system be?

You're looking for XUL.