Answers for "how to prevent back button"

prevent back button after logout

<!--just copy paste the code of your home page into another file called 
home2.html, but this file should not contain the back button--> then do 
<button onclick = "document.location = 'home2.html'">back</button>

disable back button in browser

<script type="text/javascript">  function preventBack() {window.history.forward();}  setTimeout("preventBack()", 0);  window.onunload = function () {null};</script>