Full Screen Background Image in Firefox
See this: http://www.ingress.com/
How do you do something like this that will look right in any monitor resolution? In the Ingress site, it looks like even the size of the content (the iphone image for example) scales as you shrink or grow the resolution/window size.
It's easy, but it's CSS3 and not supported on old browsers. Use
background-size:contain in your CSS.
CSS-tricks has an article with other, more robust solutions.