When your iChat AV status is Available, others who have you in their Buddy Lists see you're online and can send you messages. When a message arrives, it appears in a window on your screen.
If you want others to see you're online, but you don't want to chat, set your status to Away. Others can still send you messages, but your status will let them know that you may not answer.
If you're not actively using your computer, your status will remain as you last set it, but your friends will see that you're idle, as well as how long it has been since you last used your computer. Any message that arrives while you are away or idle will be waiting on your screen.
To prevent messages from being sent to you, or to prevent someone from seeing that you're idle, set your status to Offline. |