js无间断力片滚动 只能滚一次

Question

好几次碰上这问题，无间断却只能复制滚动一次。觉得代码应该没什么问题，实在看不出毛病所在！
请指点下，问题到底在哪？ 谢谢
<div id="demo" style=" width:600px; height:55px; overflow:hidden;">
    <table width="100%" border="0" cellpadding="0" cellspacing="5">
        <tr>
             <td id="demo1">
              <table width="75%" border="0" cellspacing="0" cellpadding="0">
        <tr>
         <td align="center"><img src="junnew_ad.jpg" width="204" height="148">&nbsp;&nbsp;<img src="junnew_new/images/junnew_ad.jpg" width="204" height="148">&nbsp;&nbsp;</td> 
      </tr>
     </table>
              </td>
              <td id="demo2" width="25%"></td>
        </tr>
    </table>
 </div>
<script type="text/javascript"> 
var speed=1
demo2.innerHTML = demo1.innerHTML
function Marquee(){
if(demo2.offsetWidth-demo.scrollLeft<=0)
demo.scrollLeft-=demo1.offsetWidth
else{
demo.scrollLeft++
}
}
var MyMar=setInterval(Marquee,speed)
demo.onmouseover=function() {clearInterval(MyMar)}
demo.onmouseout=function() {MyMar=setInterval(Marquee,speed)}
</script>  

Answer 1

<div id="demo" style=" width:600px; height:55px; overflow:scroll;"> 
    <table width="601px" border="1" cellpadding="0" cellspacing="5"> 改成这样试试能看出原因来不？

Answer 2

谢谢，明白了是图少的原因
demo2.offsetWidth-demo.scrollLeft <=0   这个条件达不到