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

This seems to accomplish what you're going for.

#left {
  float:left;
  width:180px;
  background-color:#ff0000;
}
#right {
  width: 100%;
  background-color:#00FF00;
}

  

    left
  
  

    right