Why does Twitter use a hash and exclamation mark in URLs, and how do they rewrite search URLs?

Question

We understand the hash is for AJAX searches, but the exclamation mark? Anyone know?

Also, the \"action\" attribute for their search form points to \"/search,\" but

Answer 1

To answer the second part then: It is redirecting you to /#!/search.

If you look at the response headers when going to http://twitter.com/britishdev (plug plug) you are returned a 302 (temporary redirect) with the Location header set as "Location: http://twitter.com/#!/britishdev"

Yes JavaScript is then pulling all your detail in on the destination page but regardless that is where you are redirected to.