you should then try http://liveweave.com. they have code-hinting for HTML5, CSS3, JS, jQuery...really awesome stuff. I recently found it, and loving it so far.
JSFiddle has had this for a while.
But for .NET, that's what makes it neater. JSFiddle collab has been helpful, now we have it in .NET too :D
Good for GUI, but for business logic we need the real deal :).