Om filerna heter bild1.jpg, bild2.jpg, osv och miniatyrerna bild1_mini.jpg, bild2_mini.jpgosv...
<script type="text/javascript">
function bigIn(th){
document.getElementById("bigimage").src=th.src.replace(/\_mini/i, "");
}
function bigOut(){
document.getElementById("bigimage").src="placeholder.gif";
}
</script>
<img src="bild1_mini.gif" onmouseover="bigIn(this);" onmouseout="bigOut();"/>
<img src="bild2_mini.gif" onmouseover="bigIn(this);" onmouseout="bigOut();"/>
<img src="bild3_mini.gif" onmouseover="bigIn(this);" onmouseout="bigOut();"/>
...
<img src="placeholder.gif" id="bigimage">