When I go on facebook chat?

[Andrew]

Sometimes there is some lag in the update of your chat list. This especially happens if you have your Facebook account logged in in the background. Your chat goes into a frozen-like state where it's sending out a ping that you are online but, it refused to get pings from other people. Then, when you click on your Facebook window, it receives all of those pings. Basically, that person left Facebook long ago and your computer just doesn't know yet.

Try hitting the refresh button before you click on someone's name to chat, then you won't get any ghost people.