There are a lot of people who does not know what is all the symbols in the chat box mean, neither do I. So I search them up and going to let everyone know now.
The green circle means the user is currently active and is available to chat with.
The gray colour half moon means that the user is idle and have not been active in Facebook, either on the wall or chat box, for more than 10 minutes. He/she might not be available to chat.
The gray circle means that the user is offline or log out from Facebook. You would not be able to send him/her message through the chat box but you can send them message through the inbox.
If you are online and active on Facebook, but does not want anyone to prompt you on the chat box, you can always set your chat box status to offline by clicking on the option tab in the chat box list and click 'go offline'.
I also saw there are some people asking question like will Facebook automatically sign you out if you have been idle for a very long time. The answer is NO. You will just remain idle until you start to have any activity on Facebook. (I've even try once for like 8 hours, and I just remain idle for the whole night.)
Now if you have many friends in your friend list, and the chat box is getting too packed, you can always sort them to group in the 'edit friend' tab on the top right of your Facebook page. Then at the chat box list, click on the 'friend lists' tab and you can choose which group of friends you want to display in your chat list.
It's actually quite easy to figure out all these. This post is seriously meant for Facebook beginners and people who does not know much about the chat box thingy. If you know about all this stuffs, congratulation, you are a serious Facebooker and you can kindly ignore this post. :)
