404. That’s an error.
The requested URL /add?feedurl=https://dotocdovongquay-cem.khogia.net/dotocdovongquay-cem.rss was not found on this server. That’s all we know.
/add?feedurl=https://dotocdovongquay-cem.khogia.net/dotocdovongquay-cem.rss