湘潭商贸职业技术学院:JS问题,帮我解释

<script type="text/javascript">
//Enter "frombottom" or "fromtop"
var verticalpos="frombottom"
if (!document.layers)
document.write('</div>')
function JSFX_FloatTopDiv()
//more javascript:http://cfan.net.cn
{
var startX =6,
startY = 150;
var ns = (navigator.appName.indexOf("Netscape") != -1);
var d = document;
function ml(id)
{
var el=d.getElementById?d.getElementById(id):d.all?d.all[id]:d.layers[id];
if(d.layers)el.style=el;
el.sP=function(x,y){this.style.left=x;this.style.top=y;};
el.x = startX;
if (verticalpos=="fromtop")
el.y = startY;
else{
el.y = ns ? pageYOffset + innerHeight : document.body.scrollTop + document.body.clientHeight;
el.y -= startY;
}
return el;
}
window.stayTopLeft=function()
{
if (verticalpos=="fromtop"){
var pY = ns ? pageYOffset : document.body.scrollTop;
ftlObj.y += (pY + startY - ftlObj.y)/8;
}
else{
var pY = ns ? pageYOffset + innerHeight : document.body.scrollTop + document.body.clientHeight;
ftlObj.y += (pY - startY - ftlObj.y)/8;
}
ftlObj.sP(ftlObj.x, ftlObj.y);
setTimeout("stayTopLeft()", 10);
}
ftlObj = ml("divStayTopLeft");
stayTopLeft();
}
JSFX_FloatTopDiv();
</script>

d.getElementById
document.body.scrollTop
var ns = (navigator.appName.indexOf("Netscape") != -1);
var d = document;
没行都给我注释一下，谢谢，