title: Implementing logout function
body: <p>I am working on my final year project which is an web based application. I want to implement logout function in that project. But don't know how to do that. Also I want to implement auto logout functionality i.e. after a particular time period say after 20 minutes a user will be automatically logged out if he/she does not perform any action during this period. A message should be displayed to the user "Sorry, Your session has expired Please login again". How to do that?   </p>