gistfile1.htm

<!-- The cheater way -->
<a href="javascript:window.history.go(-2);">Go back 2 history</a>

<!-- The more correct way -->
<span id="go-back">Go back</span>
<script type="text/javascript">
  document.getElementById('go-back').onclick = function() {
    window.history.go(-2);
  }
</script>