js滚动为什么不能循环？

Question

我照着网上的代码写的图片循环向上滚动为什么图片滚动完了，就不循环了呢？
<div id="demo" style="overflow:hidden; height:160px; width:100px;"> 
<div id="demo1"> 
<img src="file:///F|/Web/shop/images/20081261657514003822.jpg" width="80" height="80"> 
<img src="file:///F|/Web/shop/images/p.gif" width="80" height="80"> 
<img src="file:///F|/Web/shop/images/20081261657514003822.jpg" width="80" height="80"> 
<img src="file:///F|/Web/shop/images/p.gif" width="80" height="80"> 
<img src="file:///F|/Web/shop/images/20081261657514003822.jpg" width="80" height="80"> 
<img src="file:///F|/Web/shop/images/p.gif" width="80" height="80">  
</div> 
<div id="demo2"> </div> 
</div> 
<script> 
  var speed=20 
  demo2.nnerHTML=demo1.innerHTML  
  function Marquee(){ 
    if(demo2.offsetTop-demo.scrollTop <=0)  
  demo.scrollTop-=demo1.offsetHeight 
  else{ 
  demo.scrollTop++ 
  } 
  } 
  var MyMar=setInterval(Marquee,speed) 
  demo.onmouseover=function() {clearInterval(MyMar)}//鼠标移上时清除定时器达到滚动停止的目的 
  demo.onmouseout=function() {MyMar=setInterval(Marquee,speed)}//鼠标移开时重设定时器 
</script>

Answer 1

<script type="text/JavaScript">
document.write('<div id="picrun" style="height:68px;overflow:hidden;width:290px;font-size:0">');
document.write('<span style="height:68px;overflow:hidden;width:290px;"><a id="img1" href="@[ad_link1]"><img src="http://i1.6.cn/7a/60/h450081244163854.jpg" border="0px" width="290px" height="68px"/></a></span>');
document.write('<span style="height:68px;overflow:hidden;width:290px;"><a id="img" href="@[ad_link2]"><img src="http://i2.6.cn/a5/e5/n948391244539267.jpg" border="0px" width="290px" height="68px"/></a></span>');
document.write('<span style="height:68px;overflow:hidden;width:290px;"><a id="img3" href="@[ad_link3]"><img src="http://i3.6.cn/f9/8a/k837331244192528.jpg" border="0px" width="290px" height="68px"/></a></span>');
document.write('</div>')var oMarquee = document.getElementById("picrun"); //滚动对象
var iLineHeight = 68; //单行高度，像素
var iLineCount = 3; //实际行数
var index=0;
function run() {
    oMarquee.scrollTop += Math.ceil(((index+1)*iLineHeight-oMarquee.scrollTop)*0.2);
    if ( oMarquee.scrollTop == iLineCount * iLineHeight ){
   oMarquee.scrollTop = index = 0;   
}
    var speed = 0;
    if ( oMarquee.scrollTop % iLineHeight == 0 ) {
        speed=1000;if(oMarquee.scrollTop!=0)index++;
    }
    window.setTimeout( "run()", speed);
}
oMarquee.innerHTML += oMarquee.innerHTML;
window.setTimeout( "run()", 1000 );
</script>摘抄一个给你！

Answer 2

demo2.innerHTML=demo1.innerHTML