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

.container {
  width:100%;
  display:table;
  vertical-align:middle;
}

.left {
  width:100%;
  display:table-cell;
  text-align:center;
}

.right {
  width:40px;
  height:40px;
  display:table-cell;
  float:right;
}

<div class="container">
  <div class="left">Left</div>
  <div class="right">Right</div>
</div

Try this. It worked for me.