En lille hurtig kode jeg smækkede sammen, hvor popup-billedet følger musen og er til venstre for musen (Kan selvfølgelig let ændres til dine behov :D)
<html>
<head>
<script type="text/javascript" language="javascript">
function ShowImg(e,imgsmall,imglarge){
var imglarge=document.getElementById(imglarge);
var musX = (typeof event != 'undefined') ? event.clientX : e.pageX;
var musY = (typeof event != 'undefined') ? event.clientY : e.pageY;
imglarge.style.top=musY+10;
imglarge.style.left=musX-imglarge.offsetWidth-10;
imglarge.style.display="inline";
}
function HideImg(id){
document.getElementById(id).style.display="none"
}
</script>
</head>
<body>
<p>hej</p>
<img src="img1.jpg" width="300" onmousemove="ShowImg(event,this,'img2')" onmouseout="HideImg('img2')">
<img id="img2"width="300" src="img2.jpg" style="position:absolute;display:none">
<img src="img2.jpg" width="300"onmousemove="ShowImg(event,this,'img3')" onmouseout="HideImg('img3')">
<img id="img3"width="300" src="img1.jpg" style="position:absolute;display:none">
</body>
</html>