Facebook is a social networking website that offers every registered member the opportunity to send, receive, and archive private messages. This feature works similarly to an e-mail inbox where you can check for any new messages from other users. View your Facebook message list to see at a glance which messages you have already read so you can archive them or focus on the ones you have not read.
Log into your Facebook account.
Click the "Messages" link on the sidebar of your home screen to see your recent private messages and chat history.
Look at the message items that do not have a grey background. Message threads that you have previously read have a white background.