Many people find it annoying when a user types entirely in capitals.
Don't join a chatroom and then leave without saying something It is considered impolite to enter a chatroom and then leave without saying something. When you are in a chatroom, do take part in the conversation. If you are going to be away from your computer for a short time, tell the other users. Remember that this is a person and they may have other things to do at the same time. In some chatrooms it could be considered a flood and you might be kicked out.