var nm = 16;
var sstr = "/img_2/menu";
var eos = ".jpg";
var browserMozilla	= navigator.userAgent.toLowerCase().indexOf("gecko") != -1;

imgs = new Array(nm*2);

for (i = 1; i <= nm*2; i++) {
	imgs[i] = new Image(); imgs[i].src = sstr + i + eos;
}

function getSourceElement(event) {
	var event = (browserMozilla) ? event : window.event;
	return srcEl = (browserMozilla) ? event.target : event.srcElement;;
}

function change(event, m) {
	if (srcEl.tagName != "IMG") return true;
	var str = event.src;
	var i = str.indexOf(sstr);
	if (i == -1) return true;
	var n = parseInt(str.substring(str.length-4, i + sstr.length)) + m;
	event.src=imgs[n].src;
}

function over(event) { change(getSourceElement(event), 1); }
function out(event) { change(getSourceElement(event), -1); }