gistfile1.js

<script type="text/javascript" src="https://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js"></script>
<script type="text/javascript">

  $(document).ready(function(){
   
      var timer;

      function changeIndex(){
      $('li').each(function(i){
        //console.log($(this).width());
        //change z-index on every hover
          $(this).css('z-index',Math.floor(Math.random() * 30));
        });

      }

      $('#holder').hover(function(){
           timer = setInterval(changeIndex, 100);
      }, function(){
        //reset to stop and set z-index back to 0 on all
        //this makes the last image always show first
        clearInterval(timer);

        $('li').each(function(i){
          $(this).css('z-index',0);
        });

      });

	});
</script>