Why exclamation is used in URLs? [duplicate]

Question

Possible Duplicate:
What's the shebang (#!) in Facebook and new Twitter URLs for?

Hi

I was just wondering what is the use of "!" in urls like this

http://www.facebook.com/profile.php?id=xxxxxxxx&v=wall#!/profile.php?id=yyyyyy&v=wall

I know Facebook uses #(hash) for changing the query string parameters with JavaScript but what is the meaning of exclamation (!), why it is used after # ? We can even work with # only to change the querystring params. Is there any benefit of using ! ? or any other thing is there which I am missing ?

Answer 1

It's because it is an AJAX crawlable notation for URLS, an effort driven by Google to define a convention allowing Web 2.0 websites to be indexed by search engines.

And of course check the perfectly valid answer for What's the Shebang in the new Facebook and Twitter URLs?