anvas because 'writing-mode' is set to 'vertical-rl'.">

  <style>
  img
    {
      margin-left: 100px;
    }

  iframe
    {
      border: transparent 0px none;
      height: 100px;
      vertical-align: top;
      width: 250px;
    }

  img#reference-overlapped-red
    {
      bottom: 100px;
      position: relative;
      z-index: -1;
    }
  </style>
 </head>

 <body>

  <p>Test passes if there is a filled green square and <strong>no red</strong>.</p>

  <div><iframe src="support/embedded-doc-for-backg