Chatting on Your iPhone
Why might you want to see who is online? So you can chat with them, of course. To that end, you can easily access Facebook's real-time text chat from your iPhone.
Start by tapping the Menu button to go to the applications screen; then tap the Chat button. This displays a list of your friends who are currently online. Those friends available for chat have a green dot next to their names; those who are "asleep" or otherwise unavailable have a crescent moon instead.
To initiate a chat session, tap that person's name. The chat screen now appears; use the onscreen keyboard to enter your initial message and then tap the Send button. Your ongoing conversation will display in the top of the window.
Figure 14 Participating in a chat session