<!DOCTYPE>
<html>
<head>
  <title>Opacity and positioning</title>
  <style type="text/css" media="screen">
    .container {
      position: relative;
      height: 120px;
      width: 120px;
      padding: 10px;
      margin: 50px;
      -webkit-box-sizing: border-box;
      border: 1px solid black;
    }
    
    .child {
      height: 100px;
      width: 100px;
      opacity: 0.8;
      background-color: red;
    }
    
    .inner {
      position: absolute;
      width: 100px;
      height: 100px;
      background-color: green;
    }
    
    .compositing {
      -webkit-transform: translateZ(0);
    }
  </style>
</head>
<body>
<p>You should see two green boxes below, with no red</p>

<div class="container">
  <div class="child">
    <div class="inner"></div>
  </div>
</div>

<div class="container">
  <div class="child">
    <div class="inner compositing"></div>
  </div>
</div>

</body>
</html>