To whom it may,

Hi there,
A bit new to flash but I came across this site and was wondering how they did the background image. I noticed it detects the screen resolution so that the background always follows how-ever big your browser window is...How is this achieved???? Is this done in flash? I really like the effect it has...

Here's the link...
http://www.roughroses.com/


I appreciate your help,
Malone11235