title: Crossbrowser onbeforeunload?
body: <p>Does <a href="https://developer.mozilla.org/En/DOM/Window.onbeforeunload" rel="noreferrer"><code>window.onbeforeunload()</code></a> fire in all browsers? I need a onbeforeunload functionality which is supported at least by IE6 and FF3.6. </p>
  
  <p>For IE, <code>onbeforeunload()</code> seems only to be <a href="http://msdn.microsoft.com/en-us/library/ms536907%28v=vs.85%29.aspx" rel="noreferrer">supported by IE9</a></p>