Browse pages while music is playing

There's a new feature开发者_JS百科 on vkontakte.ru (I bet facebook has the same, not sure though). You browse pages while player keeps playing music at the background without interruption. How is this possible?

The use Ajax (so they just load something else in the page but they don't reload it completely). Until not long ago, you could only change the hash (after the #) in the url but now, with the new history API, it is possible to change the whole url (with pushStates basically) : https://developer.mozilla.org/en/DOM/window.history

Check pjax , it's easy to use. May be that is exactly what you need.