It works for me in firefox. I dunno, I've never liked the opacity functions because of how hard it is to get them to work in all browsers. This is a simple way to set opacity in both firefox and IE:
function setOpacity(value, imgObj) {
if (window.sidebar) { imgObj.style.MozOpacity=(value/100); }
if (document.all) { imgObj.filters.alpha.opacity=value; }
}
I'll have a look at your site later and see what I can do.