<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8"/>
<title>Unique Identifier (iframe)</title>
</head>
<body>

  <div style="width: 100px; height: 500px;">
    <math><mtext style="background: red; color: white;">FAIL</mtext></math>
  </div>
  <div style="width: 100px; height: 500px;">
    <math><mtext style="background: green; color: white;"
                 id="PASS">PASS</mtext></math>
  </div>

</body>
</html>