403
Forbidden
The server understood the request but refuses to accept and serve it. The server may or may not choose to send back a reason for the rejection of the request. The client should not make the same request again.
Use Case
A client requests for a photo from a server but the photo has been banned for some reasons, so the server responds with a 403 Forbidden error. If the server wants to hide that this resource ever existed, it may return a 404 Not Found too.