$(document).ready(function() {
 var speed = 3000;
 var run = setInterval('rotate()', speed);
 });
 function rotate() {
 var item_width = $('#viewport li').outerWidth();
 var left_value = 0;
 var left_indent = parseInt(parseInt($('#viewport ul').css('left')) - item_width);
 $('#viewport ul').animate({'left' : left_indent}, 1000, function () {
 //move the first item and put it as last item
 $('#viewport li:last').after($('#viewport li:first'));
 //set the default item to correct position
 $('#viewport ul').css({'left' : left_value});
 });
 //cancel the link behavior
 return false;
 }