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(tab.scrollLeft<=0) 
tab.scrollLeft+=tab2.offsetWidth 
else{ 
tab.scrollLeft-- 
} 
} 
var MyMar=setInterval(Marquee,speed); 
tab.onmouseover=function() {clearInterval(MyMar)}; 
tab.onmouseout=function() {MyMar=setInterval(Marquee,speed)}; 