This is a simple example using Push and Popstate. This practice is becoming more common throughout sites such as Twitter and Facebook for changing a URL within the address bar without reloading another page. Typically this allows users to bookmark or share URLs when sites are using some type of infinite scroll.
This widget lets you search for users to @mention in your posts. It works very much like Facebook and Google+ in that it supports users with spaces in their name. It writes to a hidden field with the user ID's formatted in this way: @ [12345] while showing @username in the input box. You can save the encoded string for easier parsing at display time.