title: Custom dialog box to get confirmation when browser tab is closed
body: <blockquote>
    <p><strong>Possible Duplicate:</strong><br>
    <a href="https://stackoverflow.com/questions/2132760/how-to-ask-confirmation-when-closing-a-window">How to ask confirmation when closing a window?</a>  </p>
  </blockquote>
  
  
  
  <p>I would like to display a confirmation box and a custom message when the browser tab is closed. Users can click OK to actually close the tab, and CANCEL to stay on the page.</p>
  
  <p>The following is my code. Can someone tell me how I can make it work?</p>
  
  <pre><code>    window.onbeforeunload = function (e) {
      e = e || window.event;
  
      // For IE and Firefox prior to version 4
      if (e) {
          e.returnValue = 'ARE you sure?';
      }
  
      // For Safari
      return 'ARE you sure?';
  };
  </code></pre>