垂直导航条下面有2个三角，尖头向下的鼠标放上去，导航就向下滚。向上反之。这样的代码怎么写？

自己测试吧注意右边的滚动条把span换作img控件就可以了
<html>
<head>
<SCRIPT LANGUAGE="JavaScript">
<!--
var j
function up()
{
window.scrollBy(0,-10)
setDiv()
j=window.setTimeout("up()",10)
}
function down()
{
window.scrollBy(0,10)
setDiv()
j=window.setTimeout("down()",10)
}
function setDiv()
{
var div=document.getElementById('test')
div.style.pixelTop=document.body.scrollTop
div.style.pixelLeft=0
}
//-->
</SCRIPT>
</head>
<body onload='setDiv()'>
<form>
<div id='test' style='position:absolute'>
<span onmouseenter='up()' onmouseout='window.clearTimeout(j)'>UP</span>
<span onmouseenter='down()' onmouseout='window.clearTimeout(j)'>DOWN</span>
</div>
<div style="width:100%;height:2000px">
</div>
</form>
</body>
</html>