Session key

Status 951 expresses that a session key between the client app (ie browser) and the server has expired. The session was auto-closed. The user gets an instruction to re-initiate the page, so the browser can invoke a new session towards the browser. Often, this will result in a new login dialog to be presented for the user to log in into the application again.

This usually happens when a session time-out has passed. (such as an access to the application after a night of inactivity.)

Most browsers will invoke this reload after pressing CTRL-F5 or CMD-Shift-R or similar. Most browsers have related buttons on their icon bar.