After a preset period of inactivity Daystar iStructural.com will end the current session. The page showing at the time will still be there but if you try to save, calculate or print you will receive a warning that your session has timed out and that you will need to login. Open a new tab in the same browser and go to the login screen. Once you have logged in go back to the original tab and you will now be able to save, calculate etc.

You can set the Session Timeout on the Projects page under the Preferences menu.