title: Logout problem in html frame and codeIgniter
body: <p>I m using PHP and framework is codeigniter.
  I have put iframe to display all data.
  when I click logout link, I cleared session value and redirect to login page.
  but when again if I press back button it shows me the previous frame contain.
  and some time It display nothing on frame after press back button of browser, but if I press refresh button then it will reinitialize session and work again.
  so pleas tell me ho to destroy session in codeIgniter so if user press back button he can not visit it.</p>