title: Leave Page Stay On Page With Custom Message
body: <p>I am trying to put some custom text on the popup that asks for leave page or stay on the page.
  I tried this</p>
  
  <pre><code>window.onbeforeunload = function () {
               return "This is my custom message";
           };
  </code></pre>
  
  <p>But Mozilla and Chrome still says their own messages while IE shows my message.
  So what I am trying to do is it should show my custom message with Leave and Stay buttons.
  And I am sure I have seen in some webiste although I don't remember which website :(</p>
  
  <p>Is it possible?</p>