//<!-- beatiful, clean and working ;-)
if(document.images){
	var imgon  = new Image(); imgon.src  = "loucb.gif";
	var imgoff = new Image(); imgoff.src = "louca.gif";
	}
function ukaOn(imgName) {
	eval('document.images["'+imgName+'"].src = imgon.src');
	} 
function ukaOff(imgName) {
	eval('document.images["'+imgName+'"].src = imgoff.src');
	}
//-->