When you log out, log out completely…

Closing or minimizing your browser or typing in a new web address when you're done using your online account may not be enough to prevent others from gaining access to your account information. Instead, click on the "log out" button to close your account and terminate your online session, and then close (X out of) your browser. In addition, don't permit your browser to "remember" your username and password information. If this browser feature is active, anyone using your computer will have access to your personal account information.   Source: SANS Institute & OnGuardOnline.gov