It is your broswer that controls whether you are "logged in" to the CAHSEE site. Consequently, there is no direct way for this site to force you to "log out".
One method is to simply quit your browser; that should log you out.
Alternatively, there is a somewhat
roundabout method that causes most browsers to forget your login
information; if you want to try that,
click here.This will pop up a new login dialog.