http://airolusion.com/wpscripts/jsRollover.js

1rolls = new Array(); numRolls=0;
2
3function PPFindObj(n, d) {
4  var p,i,x;
5  if( !d ) d=document; 
6  if((p=n.indexOf("?"))>0&&parent.frames.length) { d=parent.frames[n.substring(p+1)].document; n=n.substring(0,p); }
7  if( !(x=d[n])&&d.all ) x=d.all[n]; 
8  for( i=0;!x&&i<d.forms.length;i++ ) x=d.forms[i][n];
9  for( i=0;!x&&d.layers&&i<d.layers.length;i++ ) x=PPFindObj(n,d.layers[i].document); 
10  return x;
11}
12
13function PPImgFind(name) {
14  if (document.images)
15    for(var i=0;i<numRolls;i++)
16      if( name == rolls[i].name ) return rolls[i];
17  return null;
18}
19
20function PPImgAction( action, name, roll ) {
21  if( !roll ) roll = PPImgFind(name); var obj = PPFindObj(name); if (roll && obj)
22  {
23    if( action == 'over' ) obj.src = roll.down ? roll.imgDownOver.src : roll.imgOver.src;
24    else if( action == 'out' ) { obj.src = roll.down ? (roll.radio ? roll.imgDown.src : roll.imgNormal.src) : roll.imgNormal.src; if(!roll.radio) roll.down = false; }
25    else if( action == 'down') {
26      roll.down = true; PPImgAction('over',name,roll);
27      if( roll.radio ) {
28        for( var i=0;i<numRolls;i++ )
29          if( rolls[i].radio && rolls[i].name != name ) { rolls[i].down=false; PPImgAction('out',rolls[i].name,rolls[i]);}}
30      }
31      else if(action =='up') { if(!roll.radio) {roll.down = false; PPImgAction('over',name,roll);}}
32}}
33
34function PPImg( name,normal,over,down,downover,initDown,radio ) {
35  this.name = name;
36  this.imgNormal = new Image(); this.imgNormal.src  = normal; 
37  this.imgOver = new Image(); this.imgOver.src  = over; 
38  this.imgDown = new Image(); this.imgDown.src  = down; 
39  this.imgDownOver = new Image(); this.imgDownOver.src = downover; 
40  this.down = initDown; this.over = false; this.radio = radio;
41}
42
43function PPImgInit( name,normal,over,down,downover,initDown,radio ) { if (document.images) rolls[numRolls++] = new PPImg(name,normal,over,down,downover,initDown,radio); }