404. That’s an error.
The requested URL /add?feedurl=http://maydodorung-aco.sieuthithietbido.com/maydodorung-aco.rss was not found on this server. That’s all we know.
/add?feedurl=http://maydodorung-aco.sieuthithietbido.com/maydodorung-aco.rss