请问一个Mousemove的问题

Question

<style>
<!--
#leftright, #topdown{
position:absolute;
left:100;top:50;width:1px;
height:1px;
layer-background-color:black;
background-color:black;
z-index:50;
font-size:1px;
}
-->
</style>
<div id="leftright" style="width:expression(document.body.clientWidth-200);left:-100"></div>
<div id="topdown" style="height:expression(document.body.clientHeight-100);top:-100"></div>
<script language="JavaScript1.2">
if (document.all&&!window.print)
{
leftright.style.width=document.body.clientWidth-100
topdown.style.height=document.body.clientHeight-100
}function followmouse1(){
leftright.style.pixelTop=document.body.scrollTop+event.clientY+1topdown.style.pixelTop=document.body.scrollTop+event.clientY+1-100
if (event.clientX<document.body.clientWidth-2){
leftright.style.pixelLeft=document.body.scrollLeft+event.clientX+1-100
topdown.style.pixelLeft=document.body.scrollLeft+event.clientX+1
}else{
leftright.style.pixelLeft=document.body.clientWidth-2-100
topdown.style.pixelLeft=document.body.clientWidth-2
}
}function followmouse2(e){
document.leftright.top=e.y+1
document.topdown.top=pageYOffset
document.topdown.left=e.x+1
}if (document.all)
document.onmousemove=followmouse1
else if (document.layers){
window.captureEvents(Event.MOUSEMOVE)
window.onmousemove=followmouse2
}function regenerate(){
window.location.reload()
}
function regenerate2(){
setTimeout("window.onresize=regenerate",400)
}
if ((document.all&&!window.print)||document.layers)
window.onload=regenerate2
</script>