Popular "effect",anyone know how it's done?

I’ve been trying to duplicate this effect for awhile now, but I’m not making any progress and I can’t seem to find any good tutes out there.

Here is a good example of what I’m talking about…

http://www.viaduct.co.uk/viaduct.html

What I’m referring to is the fullscreen flash “background” that resizes with the window, and how the other elements ( like the nav and arrow on the right ), do not resize, but rather just move with the window.

I’m feeling a bit stupid because it seems like this is used commonly, but it completely has me stumped.

anyone?