scrollLeft的相关问题（js横向无缝滚动）

<div id="demo">
<div id="innerdemo">
<div id="demo1">
<img src="images/0.jpg" />
<img src="images/1.jpg" />
<img src="images/2.jpg" />
<img src="images/3.jpg" />
<img src="images/4.jpg" />
<img src="images/5.jpg" />
</div>
<div id="demo2"></div>
</div>
</div>

#demo{ width:600px; height:200px; border:1px solid #CCC; margin:20px auto; overflow:hidden;}
#innerdemo{ width:800%; }
#demo1,#demo2{float:left;}

function crossMarquee(){
var speed=10;
var oDemo=document.getElementById("demo");
var oinnerDemo=document.getElementById("innerdemo");
var oDemo1=document.getElementById("demo1");
var oDemo2=document.getElementById("demo2");
oDemo2.innerHTML=oDemo1.innerHTML;
function Marquee(){
if(oDemo1.offsetWidth<=oDemo.scrollLeft){
oDemo.scrollLeft-=oDemo1.offsetWidth;
}else{
oDemo.scrollLeft++;
}
}
var myMar=setInterval(Marquee,speed);
oDemo.onmouseover=function(){clearInterval(myMar);}
oDemo.onmouseout=function(){myMar=setInterval(Marquee,speed);}
}
window.onload=function(){
crossMarquee()

};