There are two ways to appear offline to someone, permanently.

1. Here’s how to go and block them right now:
   1. Click the down-arrow on the right end of the New button and select Chat to open a chat tab.
   2. In the To: field, enter the ID of the person you’d like to block.
   3. Now, in the toolbar along the top, click Block Sender.
   4. Finish by clicking the x to close the tab.
2. Here’s how to block someone if they try to start a chat with you:
   1. In the chat tab that they opened, click Block Sender along the top. That’s it!

Yahoo! Messenger users: If you want to block a contact who’s in your Messenger List, you’ll first have to remove them from your buddy list in the Messenger client.