Is it just facebook or your internet connection ??..
The Facebook Chat feature allows you to send and receive
messages in real time with friends who are online.
Your chat box reveals a list of available friends you can
chat with by clicking their names.
For those times when you're not up for chatting, you can
choose from several different privacy options, including disconnecting Facebook
Chat.
You can opt to disconnect it completely, or just partially allowing chat availability for certain people
and not others.
You can reconnect in a few quick steps.
Facebook Chat Availability
Your Facebook Chat availability determines how you appear
in your friends' chat lists.
When you're logged in to your Facebook account, your name
appears in the chat sidebars of any friends who are currently logged in.
When you set your chat preference to available, a green box
appears next to your name.
When you're available, but idle, a grey moon appears next to
your name.
When you're unavailable, your name appears without an icon.
Adjusting Chat Availability
Adjust your chat availability to control the visibility of
your name in friends' chat lists.
Sign in to your Facebook account and click the
"Chat" box in the lower right corner of any page to open your chat
list.
Click the "Options" icon in the upper right corner
of the box.
Click "Go Offline" to disconnect your chat
availability.
If you're using the Facebook Chat sidebar, click the
"Options" icon in the upper right corner of the box. Click the
"Chat" box to open the sidebar if it isn't showing up on your home
page.
Click the "Available to Chat" option to delete the
check mark, making yourself invisible and unavailable to chat. Click the
"Limit Availability" option and use the resulting pop-up to choose
which friend lists you wish to remain visible to. This allows you to chat with
some friends without others knowing you're logged on.
Disconnected Facebook Chat
Once you disconnect Facebook Chat or limit your chat
availability, your online presence will be invisible to other users.
You can still browse the Facebook site as you would
normally.
The appearance of your chat list won't be altered by your
availability; you'll still be able to see which of your friends are online and
available to chat.
That is, as long as their chat availability isn't hidden or
disconnected.
Your Chat Messages
If a friend attempts to message while your Facebook Chat is
disconnected, the message will be delivered to your Facebook inbox.
You'll receive an on-site notification, as well as text or
email notifications if you're set up for that, alerting you that you have a new
message in your inbox.
Click the "Message" icon that appears in the upper
left corner of any page upon signing in to your Facebook account.
Any new messages will appear in the drop-down list. Click
the "See All Messages" link at the bottom of the box to access your
inbox and respond to any messages.
http://www.facebook.com/help/?topic=chat
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