<!DOCTYPE html>
<!--
 | This is a simple z-index test.  The blue box should appear in front of
 | the green box which should appear in front of the red box.
 |   https://www.w3.org/TR/CSS21/visuren.html#z-index
 -->
<html>
<head>
  <style>
    .red, .green, .blue {
      position: absolute;
      width: 100px;
      height: 100px;
    }
    .red {
      left: 0px;
      top: 0px;
      background-color: rgb(255, 100, 100);
      z-index: 1;
    }
    .green {
      left: 30px;
      top: 30px;
      background-color: rgb(100, 255, 100);
      z-index: 2;
    }
    .blue {
      left: 60px;
      top: 60px;
      background-color: rgb(100, 100, 255);
      z-index: 3;
    }
  </style>
</head>
<body>
  <div class="blue"></div>
  <div class="green"></div>
  <div class="red"></div>
</body>
</html>