title: HTML4 and HTML5 - How can I tell if there is a `Back` state available without navigating?
body: <p>Is it possible to tell if there is a <code>back</code> state available (i.e. if the back button in the browser is clickable) without navigating?</p>
  
  <p>Id like to be able to do this in HTML4 and HTML5 if possible.</p>
  
  <p>I can see theres <code>window.history.length</code>, but it doesn't seem to have coherent or consistent behaviour.</p>
  
  <p>Is this possible?</p>
  
  <p>I can see there is this thead, but its rather old. Was wondering if there were HTML5 changes since this thread: <a href="https://stackoverflow.com/questions/3588315/how-to-check-if-the-user-can-go-back-in-browser-history-or-not">How to check if the user can go back in browser history or not</a></p>