在线等待，如何在浮动图片上加入动作！

<body>
<div style=height:1000></div>
<script>
suspendcode="<DIV id=yuzi style='right:16px;POSITION:absolute;TOP:1px;'><img border=0 src='img/down.gif' onClick='scrollit()'></div>"
document.write(suspendcode);
lastScrollY=0;
function heartBeat(){
diffY=document.body.scrollTop;
percent=.1*(diffY-lastScrollY);
if(percent>0)percent=Math.ceil(percent);
else percent=Math.floor(percent);
document.all.yuzi.style.pixelTop+=percent;
lastScrollY=lastScrollY+percent;
}
window.setInterval("heartBeat()",1);
</SCRIPT><script LANGUAGE=JavaScript>
<!-- Begin
function scrollit() {
for (I=750; I>1; I=I-1){
scrollBy(0,1)
}
}
// End -->
</script>