Image grows with browser width?

Image grows with browser width?

Heee, I had a question; does anybody know how you can let a background
image grow with the browser in terms of Width and perhaps height as well.
What do i mean? I have two great examples here;
1 http://www.google.com/nexus/7/
2 http://getbootstrap.com/examples/carousel/
That is kinda what I'm looking for... For now my image only stays
centered.. *I don't use bootstrap I made my own responsive design in css.
#heat{
background: url(../img/full.jpg) 50% 0 no-repeat;
position: absolute;
height: 100%;
width: 100%;
margin: 0 auto;
padding: 0;
}