That's javascript... the function is in the source:
HTML Code:
<script type="text/javascript">
//<![CDATA[
function lightup(imageobject, opacity){
if (navigator.appName.indexOf("Netscape")!=-1&&parseInt(navigator.appVersion)>=5)
imageobject.style.MozOpacity=opacity/100
else if (navigator.appName.indexOf("Microsoft")!=-1&&parseInt(navigator.appVersion)>=4)
imageobject.filters.alpha.opacity=opacity
}
//]]>
</script>