Chat with any Yahoo! Mail or Yahoo! Messenger user who’s currently online. All of your contacts who are currently online will appear in your Contacts list on the left side of the screen:

If you would like to chat with someone who is not on your contacts list, you can select the New Chat link at the bottom of your contacts list. You will be prompted to enter the person's Yahoo! or Window's Live email address.

For more information about how to start a chat, click here.

For information about how to block someone, click here.