How To Log Out
After you are finished with your changes to the website, click the Log Out button at the bottom of the page.
Login Timeout
Your IIS Web Server may be configured to automatically log you out after a period of time. This feature is enabled by default (this is called session expiration) after 20 minutes of inactivity. Inactivity is time between clicking a link or a button.
So be aware that typing into a text box is seen by your IIS web server as "inactivity time" even though you might be very productive typing in inspirational and thought-provoking prose. If you type for twenty-one minutes then click the Save Changes button, guess what? Your work is gone.
The lesson is: Save Your Work Often.