Want to understand how this url and back button is working

Question

Possible Duplicate:
Facebook and Ajax
Change URL from Javascript like facebook does

IN facebook, it is not loading the full page when you click on links in most of cases, such as clicking on my wall or Photos link, but it change the Url, for example:
http://www.facebook.com/amrelgarhy?sk=wall
http://www.facebook.com/amrelgarhy?sk=photos

And when the I click on browser back button, it change the Url and goes back on the correct view.

I want to understand how facebook is doing that, are they reading the Url using javascript when backbutton clicked and load the view based on the url or what is the case?

I am asking because I am doing an ajax website and want to do something the same as what facebook is doing regarding backbutton and urls.

Answer 1

You are able to manipulate the has value at the end of the URL like this:

var hashVal = 'somevalue'; window.location.hash = '#' + hashVal;

And then the url will become www.something.com/#somevalue