无缝滚动js代码

<style type="text/css">
        #demo
        {
            background: #FFF;
            overflow: hidden;
            border: 1px dashed #CCC;
            width: 500px;
        }
        #demo img
        {
            border: 3px solid #F2F2F2;
        }
        #indemo
        {
            float: left;
            width: 800%;
        }
        #demo1
        {
            float: left;
        }
        #demo2
        {
            float: left;
        }
    </style>
    向左滚动
    <div id="demo">
        <div id="indemo">
            <div id="demo1">
                <a href="#"><img src="TestImages/12460764740.jpg" alt=""border="0" /></a>
                <a href="#"><img src="TestImages/12460764741.jpg" alt=""border="0" /></a>
                <a href="#"><img src="TestImages/12460764742.jpg" alt=""border="0" /></a>
                <a href="#"><img src="TestImages/12460764743.jpg" alt=""border="0" /></a>
                <a href="#"><img src="TestImages/12460764744.jpg" alt=""border="0" /></a>
            </div>
            <div id="demo2">
            </div>
        </div>
    </div>
        <script type="text/javascript">
            var speed = 10; //数字越大速度越慢 
            var tab = document.getElementById("demo");
            var tab1 = document.getElementById("demo1");
            var tab2 = document.getElementById("demo2");
            tab2.innerHTML = tab1.innerHTML;
            function Marquee() {
                if (tab2.offsetWidth - tab.scrollLeft <= 0)
                    tab.scrollLeft -= tab1.offsetWidth
                else {
                    tab.scrollLeft++;
                }
            }
            var MyMar = setInterval(Marquee, speed);
            tab.onmouseover = function () { clearInterval(MyMar) };
            tab.onmouseout = function () { MyMar = setInterval(Marquee, speed) }; 
    </script>