<html>
  <style>
    #green {
      margin-top: 50px;
      background-color: green;
      margin-bottom: 60px;
      min-height: 20px;
    }
    #blue {
      background-color: blue;
      margin-top: 50px;
      position: absolute;
      top: 0;
      width: 50px;
      height: 50px;
    }
    #yellow {
      background-color: yellow;
      width: 50px;
      height: 50px;
    }
  </style>
  <body>
    <div id=green>
    	<div id=blue></div>
    </div>
    <div id=yellow></div>
  </body>
</html>