What does this untypical link format '#!'

Question

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

Hello,

One thing that took my attention in some modern websites is the presence of '#!' symbols in their links, see for example twitter and Rapidshare links:

http://twitter.com/#!/SolidSnakeGTI
http://twitter.com/#!/SolidSnakeGTI/followers
http://twitter.com/#!/SolidSnakeGTI/following
This behavior is obvious when you're logged in twitter

http://rs431tl3.rapidshare.com/#!download|46311|44541812469|fairy_tgail_045_sd.mp4

What does these symbols mean, what it's called, how it works!?

Appreciated in advance Abdelrahman

Answer 1

It's all about making AJAX applications crawlable.