404. That’s an error.
The requested URL /add?source=atgs&feedurl=http://thongtin123.com/public-rss/rssid&cid=16&title=tong-hop.rss was not found on this server. That’s all we know.
/add?source=atgs&feedurl=http://thongtin123.com/public-rss/rssid&cid=16&title=tong-hop.rss