Getting a background image to scale to 100% of the viewer’s browser window width and height is tricky. Pure CSS or even CSS3 do a good job in many browser but fail in IE6, IE7 and even IE8. Opera and others fail depending on how you do it with CSS.
jQuery steps up to the plate and solves it. Well, almost. Just one little niggle. If you can live with it then this is the solution for you in all browser except IE6.