请帮忙看看下面这段代码

[chenhuizhi]

这是作一个可拖动的层，但是拖动的很不自如。由于是从网上copy，部分代码不懂意思，请告知；



drag = 0
move = 0
function mouseUp() {
move = 0
}
function mouseDown() {
clickleft = window.event.x - parseInt(dragObj.style.left)
clicktop = window.event.y - parseInt(dragObj.style.top)
dragObj.style.zIndex += 1
move = 1
}
function mouseMove() {
if (move) {
dragObj.style.left = window.event.x - clickleft
dragObj.style.top = window.event.y - clicktop

}
}

function Show(divid) {
divid.filters.revealTrans.apply();//什么意思
divid.style.visibility = "visible";
divid.filters.revealTrans.play();//什么意思
}
function Hide(divid) {
divid.filters.revealTrans.apply();//什么意思
divid.style.visibility = "hidden";
divid.filters.revealTrans.play();//什么意思
}
//-->
</SCRIPT>
<DIV id=READ style="FILTER: revealTrans(transition=23,duration=0.5) blendTrans(duration=0.5); LEFT: 100px; POSITION: absolute; TOP: 75px; WIDTH: 600px; Z-INDEX: 10">////什么意思
<div align="center">
<center>
<table width="90%" border=1 cellpadding="0" cellspacing="0" bordercolorlight="#5E9BF7" bordercolordark="#FFFFFF" >
<tr bgcolor="#ffedc8">
<td colspan="1"><DIV onmouseup="mouseUp()" onmouseout="move=0" onmousedown="dragObj=READ;mouseDown()" onmousemove="mouseMove()">标题栏 </div>
<td width=1%><A href="javascript:void(Hide(READ))">■</A>
<tr>
<td colspan="4" bgcolor=#cccccc>
<table width=100% border=0 cellspacing=4>
<tr>
<td>
<font color=Blue>一个可以拖动和关闭的层，有意思的是它每次关闭的效果都不一样。一个可以拖动和关闭的层，有意思的是它每次关闭的效果都不一样。一个可以拖动和关闭的层，有意思的是它每次关闭的效果都不一样。
</table>
</table>
</div>

[心云意水]

试试看这个，很短。
<span style='position:absolute;width:200;height:200;background:blue;color:#ffffff;cursor:hand' onmousedown=MouseDown(this) onmousemove=MouseMove() onmouseup=MouseUp()>aa</span>
<script>
var Obj
function MouseDown(obj){
Obj=obj
Obj.setCapture()
Obj.l=event.x-Obj.style.pixelLeft
Obj.t=event.y-Obj.style.pixelTop
}
function MouseMove(){
if(Obj!=null){
Obj.style.left = event.x-Obj.l
Obj.style.top = event.y-Obj.t
}
}
function MouseUp(){
if(Obj!=null){
Obj.releaseCapture()
Obj=null
}
}
</script>