<script language="JavaScript">  
if (document.images) {            
img1on = new Image();       
img1on.src ="меняем на свою";      
img1off = new Image();          
img1off.src = "меняем на свою";      
}  
function imgOn(imgName) {  
if (document.images) {  
document[imgName].src = eval(imgName + "on.src"); }}//osw  
function imgOff(imgName) {  
if (document.images) {  
document[imgName].src = eval(imgName + "off.src"); }}  
</script>  
<a href="http://fantasyflash.ru" onmouseover="imgOn('img1')"; onmouseout="imgOff('img1')" >  
<img src="http://fantasyflash.ru/avatar/ava_cat/image/cat15.jpg" border="0" name=img1></a>  
</center>