var speed=20//速度数值越大速度越慢 
  demo2.innerHTML=demo1.innerHTML 
  function Marquee(){ 
  if(demo.scrollLeft<=0) 
  demo.scrollLeft+=demo2.offsetWidth 
  else{ 
  demo.scrollLeft-- 
  } 
  } 
  var MyMar=setInterval(Marquee,speed) 
  demo.onmouseover=function() {clearInterval(MyMar)} 
  demo.onmouseout=function() {MyMar=setInterval(Marquee,speed)}