title: window.event !== window.event in IE
body: <p><strong>Code：</strong></p>
  
  <pre><code>&lt;html&gt;
  &lt;head&gt;
  &lt;script type="text/javascript"&gt;
    onload = function(){
      document.getElementById('btn1').onclick = function(){   
        if (window === window)  
          alert('window === window')
        else
          alert('window !== window');
  
        if (window.event === window.event)  
          alert('window.event === window.event')
        else
          alert('window.event !== window.event' );   
      }
    }
  &lt;/script&gt;
  &lt;/head&gt;
  &lt;body&gt;
  &lt;button id="btn1" &gt;click&lt;/button&gt;
  &lt;/body&gt;
  &lt;/html&gt;
  </code></pre>
  
  <p><strong>Result:</strong></p>
  
  <p>IE(i have tested IE6 - IE8) says:</p>
  
  <pre><code>window === window
  window.event !== window.event
  </code></pre>
  
  <p>All other browsers say:</p>
  
  <pre><code>window === window
  window.event === window.event
  </code></pre>
  
  <p>What's the reason for IE's response? Thanks.</p>