When you log in to Gmail through the browser (not the push mail) on the Samsung Galaxy Tablet, and what you wear is a browser's default setting (the default internet browser Samsung tab), there is no menu to logout or exit from Gmail.
If tabnya got itself may not be a problem, but how about if you happen again or come check emails using tabnya friend .. of course you have successfully logged off before returning to the tab that hers.
To be able to logout / exit Gmail using Samsung Tab Android default browser, or the way the trick is to go to the Basic HTML version
Can be seen in the following example display my gmail below
Click on Basic HTML, so it will display basic html version of Gmail page, the existing options for Logout / Sign Out