javascript实现平滑无缝滚动

#demo {
 background: #FFF;
 overflow:hidden;
 border: 1px dashed #CCC;
 width: 1280px;
 height:200px;
 }
 #demo img {
 border: 3px solid #F2F2F2;
 }
 #indemo {
 float: left;
 width: 800%;
 }
 #demo1 {
 float: left;
 }
 #demo2 {
 float: left;
 }

 <div id="demo">
 <div id="indemo">
 <div id="demo1">
 <a href="#"><img src="banner.jpg" border="0" /></a>
 <a href="#"><img src="banner2.jpg" border="0" /></a>
 </div>
 <div id="demo2"></div>
 </div>
 </div>

<script>
var speed=10;
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>