How do you get a css box to extend the entire width of the browser window?

Question

For example, if you look at Facebook, they have a short blue bar on top that extends the entire width of the browser. I thought about using width:100%; but I know that it needs to have a parent element to be able to do that.

Answer 1

One way:

<div style="position:absolute;left:0px;right:0px;height:20px">&nbsp;</div>