<div id=demo style=overflow:auto;height:180;width:200;background:#009900;color:#006600>  <table  align=top>  <tr>  <td id=demo1 valign=top>  <p>aaaaaaaaaaa</p>  <p>aaaaaaaaaaa</p>  <p>aaaaaaaaaaa</p>  <p>aaaaaaaaaaa</p>  <p>aaaaaaaaaaa</p>  <p>aaaaaaaaaaa</p>   </td>  </tr>  <tr>  <td id=demo2 valign=top></td>  </tr>  </table>  </div>  <script>  var speed=15  demo2.innerHTML=demo1.innerHTML//克隆demo1为demo2  function Marquee(){  if(demo2.offsetHeight-demo.scrollTop<=0)//当滚动至demo1与demo2交界时  demo.scrollTop-=demo1.offsetHeight//demo跳到最顶端  else{  demo.scrollTop++  //如果是横向的 将 所有的 height top 改成 width left  }  }  var MyMar=setInterval(Marquee,speed)//设置定时器  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>