title: Polling vs hidden iFrame for Ajax history
body: <p><strong>Background</strong></p>
  
  <p>Detection of hash change in the URL and fixing the forward/back button are two requirements for libraries that deal with Ajax history. There's two schools of thought for implementing these libraries. You can have a poller constantly check the URL (bad browsers don't have the onHashChange event). Or you can use a hidden iFrame to add points in your browser history. One may think the hidden iFrame is better than polling, but the hidden iFrame does not update the outer browser's URL. So if a user wanted to share her current state in the web application, she would always be sharing her initial state. </p>
  
  <p><strong>Question</strong></p>
  
  <p>Is there any technique for Ajax history that both doesn't require polling and also updates the main browser's URL?</p>