"You are not whitelisted on this server!" You can create a new profile in the launcher with the version the server is running or you will have to wait for the server to update, that may take more or less time depending of the server owners' reactivity. You can only connect to servers with the same protocol version as your client. They mean that you are running a different version than the server. If Minecraft updated recently, you might get these error messages. Outdated server!" or "Disconnected by server. These messages might appear when you click Join Server: Things will go wrong at some point, so here are some error messages and what they mean. If you are not, there is a list of common errors below to help you. Normally, you will be brought directly into the server. The server should appear on it with green bars on the right.
2.9 Java error, such as (): An error message.
2.8 "The authentication servers are currently down for maintenance.".Invalid session (Try restarting your game)" 2.2 "You are not whitelisted on this server!".