Using url with /#!/ like twitter does

Does anyone can tell me about what are urls like blablalba.com**/#!/**dasdas?

Twitter use them.

I have a problem with requesting page using AJAX, when I hit Back button, it doesn't load previous page that loaded using AJAX.

But, I saw in twitter, when you are in Timeline tab/page, and click @Mention tab, and hit Back button, it will bring you to Timelin开发者_开发问答e tab/page again not to your previous loaded page (non AJAX). is there a relation between it and url with /#!/ characters ?

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I am not familiar with Twitter, but your description reads a bit as if you were looking for Chris Coyer's screencast on using the hash fragment from JavaScript.