I have logged in on a public computer. Now I cannot find button to log out the page. Logging out from general Stackexchange leaves my account active. Cleaning history doesn't help also.
If you click on the StackExchange menu at the far left, you can choose logout from the options right beside the site. This worked for me.
Just another option: visit the
http://tex.stackexchange.com/users/logout page and click the logout button.