function add_listener(el, _event, _function)
{	if (el.addEventListener) { el.addEventListener(_event, _function, false); } 
	else if (el.attachEvent) { el.attachEvent('on' + _event, _function); } 
	else { eval("el.on" + _event + "=" + _function); }
}
//eval('el.on' + _event) = _function;