title: window.attachEvent doesn't seem to be working in IE8
body: <p>Top page:</p>
  
  <pre><code>...
  &lt;script&gt;
  if (window.addEventListener) {
   // addEventListener equivalent of code below
  } else if (window.attachEvent) {
   window.attachEvent("message", function(e) {
    if (e.origin != "page2.html") { return; }
    alert(e.data);
   });
  }
  &lt;/script&gt;
  
  &lt;iframe src="page2.html"&gt;&lt;/iframe&gt;
  </code></pre>
  
  <p>page2.html:</p>
  
  <pre><code>&lt;script&gt;
  var message = "hello!";
  parent.postMessage(message, '*');
  &lt;/script&gt;
  </code></pre>
  
  <p>This code works fine in Chrome, Firefox and Opera. Of course IE has its own way of doing things so this code doesn't work despite using its own <code>.attachEvent</code>. </p>
  
  <p>The page2.html is actually a page on another domain; I'm sending the correct P3P headers (shouldn't matter, but there's that).</p>
  
  <p>How do I find out why <code>postMessage</code> doesn't seem to be reaching the parent page?</p>