function change_opacity(id, opacity)
		{
			if (document.getElementById(id)) {
				var obj = document.getElementById(id);
			  	obj.style.filter = "alpha(opacity:"+opacity+")"; // IE
			  	obj.style.MozOpacity='0.'+opacity;
			  	obj.style.KhtmlOpacity='0.'+opacity;
			  	obj.style.opacity='0.'+opacity; // FireFox
			}
		}