<html>
  <style>
    div {
      width: 50px;
      height: 50px;
    }
    #red {
      background-color: red;
      margin-bottom: 50px;
      margin-top: 10px;
    }
    #blue {
      background-color: blue;
      margin-bottom: 60px;
      margin-top: 20px;
      position: absolute;
      top: 40px;
    }
    #green {
      background-color: green;
      margin-bottom: 50px;
    }
    #yellow {
      background-color: yellow;
    }
  </style>
  <body>
    <div id=red>
    	<div id=green></div>
    	<div id=blue></div>
    </div>
    <div id="yellow"></div>
  </body>
</html>