<script type="text/javascript">
function mouseOver() {
document.getElementById("rss").src="img1.png"
}
function mouseOut() {
document.getElementById("rss").src="img2.png"
}
</script>
<a href="lunk" onmouseover="mouseOver()" onmouseout="mouseOut()"><img src="img.png" id="rss" border="0" alt="" /></a>