if((eventName == 'mouseenter' || eventName == 'mouseleave') && !mouseEnterSupported){
            var item = mouseCache[el.id] || (mouseCache[el.id] = {});
            item[eventName] = fn;
            fn = fn.createInterceptor(checkRelatedTarget);
            eventName = (eventName == 'mouseenter') ? 'mouseover' : 'mouseout';