title: find parent of the opener iframe
body: <p>lets say we have an iframe in page test1.html</p>
  
  <pre><code>&lt;iframe src=test2.html"&gt;&lt;/iframe&gt;
  </code></pre>
  
  <p>and there is a link in test2.html:</p>
  
  <pre><code>&lt;a href="test3.html" target="_blank"&gt;open in new window"&lt;/a&gt;
  </code></pre>
  
  <p>in test3.html how can I know the parent of the opener? (that is test1.html)</p>