I am using it for an exam that displays only one question at a time on a page. As the user moves on from one question to the next, I don't wan't him to go back and re-answer an already answered question.

Though my scripts has several sanity checks that prevent internally from within my script the same question to be re-answered, I just needed some way to clear the history as an immediate but temporary fix to a flaw that I noticed in my design.

The flaw is, take for example you are in question number 2. I have navigation buttons on my page that allows me to move to the next, previous, first, or last item in the exam whose dynamic values are stored in a session. Now if a user goes back (through his browser) to re-answer question 1, when he clicks the next button, since in my session the next button points to Ques no 3, it would simply interpret the submission as an answer for Ques no 2 and not what the user thinks (that he's re-answering Ques No 1).