in the head tags somewhere place
<script language="JavaScript" type="text/JavaScript">
<!--
function Preload() {
var args = simplePreload.arguments;
document.imageArray = new Array(args.length);
for(var i=0; i<args.length; i++) {
document.imageArray[i] = new Image;
document.imageArray[i].src = args[i];
}
}
-->
</script>
in the body tag place this as an atribute
onLoad="Preload('image1.jpg', 'image2.gif', 'image3.png', ...)"
You can add as many images as you need, but I strongly recomend not to bother using an image preload script, it means that people with slow modems will have to wait for the images to download. If there are to many images people might think that the page isn't loading and will go back or even close the browser and will never return again.