Facebook provides its users several ways to stay in contact with friends and other contacts, whether you prefer sending direct, private messages or posting to the public "News Feed," which is visible to your entire Facebook network. Send instant messages to others who are currently online using Facebook's "Chat" feature.
Online Friends
Facebook Chat is a tool which allows you to chat in real-time with other friends who are online, whether using a computer or certain mobile devices. Friends appear in Facebook Chat only if they're signed into their accounts -- you can always send someone a direct message, post on his "Wall" or tag him in a "News Feed Post," but the only way you can contact a friend via chat is if he's online in some capacity.
Available vs. Idle
When you click on the Facebook's "Chat" box at the bottom, right corner of the page, you'll notice your friends divided into two categories. The first grouping of friends have green circles next to their names; the second grey, "half-moon" shapes. Friends in the former category are online and actively using their Facebook profiles, be they chatting, viewing the "News Feed" or posting on others' walls. The rest of your friends are "idle" and may or may not be using Facebook, or even sitting at their computers.
Going Offline
Someone's name not appearing in your chat list does not definitively mean he's offline. One option Facebook Chat gives you is the ability to "Go Offline" -- in other words, to remove yourself from friends' chat lists, even as you actively use the site. A key difference between Facebook's "invisible" mode and those you find on other websites is that when you "Go Offline" in Facebook, you can't use the chat feature at all.
Alternate Communication Options
If you believe that one of your friends is, in fact, online, in spite of her not appearing in your chat list, send her a direct message or post on her wall and wait for her to respond. If she responds to you within a few minutes, it's likely that she's chose to "Go Offline" from chat. Another possibility is that she's using a mobile device to access Facebook -- not all of them support "multitasking" or, for example, using chat while performing other Facebook operations.
Tags: Facebook Chat, News Feed, your friends, appearing your, appearing your chat, chat list, direct message
