So you want to use Facebook chat but don’t want some people to see your online status? Simply open up the Facebook Chat and click on Friends List. Start creating a new list called BlockList.
Once the list is created, add those friends to the list that you want to appear offline to. When the list is complete, hover your mouse to the little green icon adjacent to the list and click Go Offline. Bingo! You will now appear offline to everybody in the BlockList.
