Background doesn’t fit the screen total height.
Background-size it’s not cross browser compatible.
Background Resize 100%
I’ve made a jquery plugin to do a more smart image fit and resize. The image doesn’t get distorted and always mantain the image center positioned.
Smart Background Resize. Click here to see example, instrucctions and download.
If you want to make it with pure css, the image will get distorted but it will fit 100%
use: background-size: 100% 100%; -moz-background-size: 100% 100%;