滚动条自动滚动是怎么回事

加入如下代码到head区域：

<script language"javascript">
var currentpos,timer;
function initialize()
{
timer=setInterval("scrollwindow()",10);
}
function sc(){
clearInterval(timer);
}
function scrollwindow()
{
currentpos=document.body.scrollTop;
window.scroll(0,++currentpos);
if (currentpos != document.body.scrollTop)
sc();
}
document.onmousedown=sc
document.ondblclick=initialize
</script>