How to make a div fill a remaining horizontal space?

Question

I have 2 divs: one in the left side and one in the right side of my page. The one in the left side has fixed width and I want the one of the right side to f

Answer 1

I wonder that no one used position: absolute with position: relative

So, another solution would be:

HTML

  

  
Menu1 Menu2 Menu3

CSS

header { position: relative;  }
#left {
    width: 160px;
    height: 25px;
}
#right {
    position: absolute;
    top: 0px;
    left: 160px;
    right: 0px;
    height: 25px;
}

Jsfiddle example