function addEvent(elm, evType, fn, useCapture)
	// cross-browser event handling for IE5+, NS6+ and Mozilla 
	// By Scott Andrew 
	{
	  if (elm.addEventListener) { 
		elm.addEventListener(evType, fn, useCapture); 
		return true; 
	  } else if (elm.attachEvent) { 
		var r = elm.attachEvent('on' + evType, fn); 
		return r; 
	  } else {
		elm['on' + evType] = fn;
	  }
	}

function buttonOn(e) {
		if (window.event) {
			var img = window.event.srcElement;
		} else {
			var img = e.target;
		}
		img.className = 'on';
}

function buttonOff(e) {
		if (window.event) {
			var img = window.event.srcElement;
		} else {
			var img = e.target;
		}
		img.className = 'off';
}

function addListeners() {
		var nav = document.getElementById('nav');
		var images = nav.getElementsByTagName('img');
		for(i=0; i<images.length; i++) {
			addEvent(images[i], 'mouseover', buttonOn, false);
			addEvent(images[i], 'mouseout', buttonOff, false);
		}
}
		


addEvent(window, 'load', addListeners, false);