By design, there are two ways you might be automatically logged out of Manhattan. Both are designed to protect your account from intruders.
To further safeguard the privacy of a Manhattan classroom, users are automatically logged out if they have not clicked on a Manhattan command button for four hours. Typing a message does not reactive the timer, no matter how often you press keys. Only the act of clicking on a button or link within a Manhattan page restarts the four hour timer.
The reason for doing this is because students often access their classes from public computers in labs and libraries. If a student fails to logout and/or exit their web browser, the next person using that computer will have full access to their account.
Four hours is a long time, however as mentioned later in this manual, you should be aware of this timeout when composing an exceptionally long Manhattan message. Your server administrator can adjust this timeout server-wide to any value he thinks appropriate, but four hours seems to be a good compromise between security and convenience.
The moment someone else logs into Manhattan using your username and password, you will get logged out. If you are working within Manhattan and someone else logs in as you, the next time you click on a Manhattan command button or other hyperlink you'll get a message like "Sorry, but you have been logged out of the classroom. It's possible that someone else is using your account!"
You can use this feature to your advantage. Suppose you were working in a public computer lab and forgot to log out of Manhattan by clicking on the Log Out button. You can prevent someone from working with your Manhattan classroom from that lab computer by simply logging into the same classroom from any other computer on the Internet.
You can demonstrate this yourself, if you're comfortable with opening two windows in your web browser. Login to Manhattan, then press Ctrl-N to open a new window in your browser. Visit the login page, and enter your username/password to login from this window. Switch back to the first window, and click a Manhattan command button or link. You'll get the "You've been logged out" message.
As shown in the screenshot in The My Manhattan Page, when you first login you are shown the date and time of your last login, along with the "hostname" of the computer used when that login occurred. You should pay attention to what the message says to convince you that no one has guessed your password.