Full Screen background Question

[pucca017]

Hello to every1.
Im making a website that will fill all the browsers space. The background is a landscape and is not going to be moving at all. Depending on the resolution size of the user, the background needs to be smaller or bigger. I dont know if I need one image with different size for each resolution or if is something else I need to do.

The thing that worries me the most is how big the image has to be in order to fulfill the largest or biggest resolution.

Anyone knows whats the size of the browser without counting the tools bar and the status bar??

PD. The full screen is inside the browser. No popups or nothing will be added.