[development] Auto logout when users close browser.

Hello everybody, I have a problem with drupal 6. I want users to log out automatically, after users close the Tab of browser, or close browser. At the moment, when users close browser and then open browser again, they still logged in. I have try by edit 'session.cookie_lifetime' in 'settings.php', but it doesn't work. Thanks in advance for any ideas. -- *Nam Pham* Phone: (+84) 932 830 330 Email: + nampham@mbm.vn + allstarsmen@gmail.com Skype: nampham-mbm Yahoo: allstars_men