function addEvent(elm, evType, fn, useCapture){
// cross-browser event capture by Scott Andrew
	if(elm.addEventListener){
		elm.addEventListener(evType, fn, useCapture);
		return true;
	}else if(elm.attachEvent){
		var r = elm.attachEvent('on' + evType, fn);
		EventCache.add(elm, evType, fn);
		return r;
	}else{
		elm['on' + evType] = fn;
	}
} // end addEvent