如何实现进度条功能~~急~~~在线等~~~

<head>
<style>
<!--
#bar, #barbackground{
position:absolute;
left:0;
top:0;
background-color:blue;
}#barbackground{
background-color:black;
}-->
</style><script language="JavaScript1.2">/*
Dynamic Progress Bar- By Dynamicdrive.com
For full source, Terms of service, and 100s DTHML scripts
Visit http://www.dynamicdrive.com
*///1) Set the duration for the progress bar to complete loading (in seconds)
var duration=5//2) Set post action to carry out inside function below:
function postaction(){
//Example action could be to navigate to a URL, like following:
//window.location="http://www.dynamicdrive.com"
}
///Done Editing/////////////
var clipright=0
var widthIE=0
var widthNS=0function initializebar(){
if (document.all){
baranchor.style.visibility="visible"
widthIE=bar.style.pixelWidth
startIE=setInterval("increaseIE()",50)
}
if (document.layers){
widthNS=document.baranchorNS.document.barbackgroundNS.clip.width
document.baranchorNS.document.barNS.clip.right=0
document.baranchorNS.visibility="show"startNS=setInterval("increaseNS()",50)
}
}function increaseIE(){
bar.style.clip="rect(0 "+clipright+" auto 0)"
window.status="Loading..."
if (clipright<widthIE)
clipright=clipright+(widthIE/(duration*20))
else{
window.status=''
clearInterval(startIE)
postaction()
}
}function increaseNS(){
if (clipright<202){
window.status="Loading..."
document.baranchorNS.document.barNS.clip.right=clipright
clipright=clipright+(widthNS/(duration*20))
}
else{
window.status=''
clearInterval(startNS)
postaction()
}
}
window.onload=initializebar
</script>
</head>
<body>
<script language="JavaScript1.2">
if (document.all){
document.write('<div id="baranchor" style="position:relative;width:200px;height:20px;visibility:hidden;">')
document.write('<div id="barbackground" style="width:200px;height:20px;z-index:9"></div>')
document.write('<div id="bar" style="width:200px;height:20px;z-index:10"></div>')
document.write('</div>')
}</script>
<ilayer name="baranchorNS" visibility="hide" width=200 height=20>
<layer name="barbackgroundNS" bgcolor=black width=200 height=20 z-index=10 left=0 top=0></layer>
<layer name="barNS" bgcolor=blue width=200 height=20 z-index=11 left=0 top=0></layer>
</ilayer>
</body>