window.onload = function init(){
	var elements = document.getElementsByTagName("div");
	for (var i=0; i<elements.length; i++) {
		if (elements[i].className == "thumb") {
			elements[i].onmouseover = mouseOverThumb;
			elements[i].onmouseout = mouseOutThumb;
			setOpacity(0.5,elements[i]);
		}
	}
}

function mouseOverThumb(){
	setOpacity(1,this);
}

function mouseOutThumb(){
	setOpacity(0.5,this);
}

function setOpacity(opacity, obj) {
	obj.style.KHTMLOpacity = opacity;
	obj.style.MozOpacity = opacity;
	obj.style.opacity = opacity;
	opacity *= 100;
	opacity = (opacity == 100)?99.999:opacity;
	obj.style.filter = "alpha(opacity:"+opacity+")";
}