<!DOCTYPE html>
<html class="reftest-wait">
<head>
<title></title>

<script type="text/javascript">
//<![CDATA[

function showBug() {
  document.getElementById('x').style.width = 0;
  }

window.addEventListener("MozReftestInvalidate",
  function() {
    showBug();
    document.documentElement.className = "";
  }, false);

//]]>
</script>

</head>

<body style="width: 1000px; margin: 0; padding: 0">
  <table cellpadding="0" cellspacing="0" align="center">
    <tr>
      <td>
        <div style="background:red; WIDTH: 400px; height:400px;"></div>
        <div id="x" style="width: 600px"></div>

      </td>
    </tr>
  </table>
  <div style="position: absolute; top: 0; left: 300px; height: 400px; width: 400px; background: green; opacity: 0.9"></div>

<br/>

<div style="text-align: center;">
<form method="get" action="#">
  <input onclick="showBug(); return false;" value="Trigger Bug" type="button" />
</form>
</div>

</body>
</html>