a cool javascript image gallery

It takes me so long to find out the attribute about ' filters.revealTrans.Transition',is there any people can tell me what the exactly this meaning,but i have a good example for how to use,enjoy it:
script language=Javascript>
var tupian=new Array();
var tupianlink=new Array();
var adNum=0;

tupianlink[0]="http://upisqueen.blogspot.com/";
tupian[0]="http://bbs.caolu.org/UploadFile/2004-11/200411392145762.gif";
tupianlink[1]="http://upisqueen.blogspot.com/";
tupian[1]="http://bbs.caolu.org/UploadFile/2004-11/200411392145762.gif";
tupianlink[2]="http://upisqueen.blogspot.com/";
tupian[2]="http://bbs.caolu.org/UploadFile/2004-11/200411392145762.gif";
tupianlink[3]="http://upisqueen.blogspot.com/";
tupian[3]="http://bbs.caolu.org/UploadFile/2004-11/200411392145762.gif";
var currentimage=new Array();
for (i=1;i<=4;i++)
{
currentimage[i]=new Image();
currentimage[i].src=tupian[i];
}
function setCo()
{
if (document.all)
{
tupianrotator.filters.revealTrans.Transition=Math.floor(Math.random()*23);
tupianrotator.filters.revealTrans.apply();
}
}
function playCo()
{
if (document.all) tupianrotator.filters.revealTrans.play()
}
function nextAd()
{
if(adNum else adNum=0;
setCo();
document.images.tupianrotator.src=tupian[adNum];
playCo();
theTimer=setTimeout("nextAd()", 4000);
}
function linkurl()
{
jumpUrl=tupianlink[adNum];
jumpTarget='_blank';
if (jumpUrl != '')
{
if (jumpTarget != '')window.open(jumpUrl,jumpTarget);
else location.href=jumpUrl;
}
}
function listMsg()
{
status=tupianlink[adNum];
document.returnValue = true;
}
document.write('');
document.write('');