When you set up your ACC buddy list, you can see which of your buddies are currently logged into ACC so you can send Private Messages or quickly set up a trade with them (Trading Post is AC:GC only). ACC Buddies who are logged on the site when you sign in are shown at the top of the left hand navigation menu.
* Buddies with a green light next to their name are currently logged into ACC, so they're right here to receive a trade request or a private message.
* Buddies with a yellow light next to their name have been idle on ACC for more than 5 minutes. They're still logged in, but may be away from their computer.
You can also minimize or close the Buddy alert with the buttons next to "ACC Buddies". You can also quickly go to the list of all your ACC Buddies by clicking Edit Buddy List. If you want to get rid of your Buddy List from the sidebar, simply go to "My Profile" then "Edit Profile", and under Account Settings, unclick "Show online buddy list".
Check out the My Buddies section for instructions on setting up your Buddy List.