<html>
  <style>
    div {
      width: 50px;
      height: 50px;
    }
    #blue {
      background-color: blue;
      margin-top: 50px;
      overflow: hidden;
      top: 50px;
    }
    #yellow {
      background-color: yellow;
      height: 60px;
      margin-top: 30px;
    }
    #green {
      background-color:  green;
      height: 70px;
      margin-top: 50px;
    }
  </style>
  <body>
    <div id=green>
      <div id=blue>
	<div id=yellow></div>
       </div>
     </div>
  </body>
</html>