100% width background image with central site

I want to achieve something like this page:

http://codex.wordpress.org/Pages

Where the background images are 100% width to fit the size of the browser window, but the content divs are a fixed width and central.

How do I do this?

Found the answer. For anyone who searches for this,

Solution here:

http://csscreator.com/node/29182

Best wishes