title: Login session is not getting nullified
body: <p>I have a login page, in this page a login session is assigned on successfully authenticating the user and this session is being used in all the pages throughout the project. In all the pages, I have put a condition</p>
  
  <pre><code>If(Session["login"]) == null)
      Response.Redirect("login.aspx");
  </code></pre>
  
  <p>Moreover, I'm also nullifying the session at logout.
  However, this code is not working.
  On clicking back button the application is getting logged in again.</p>
  
  <p>Please anyone can help me in this.</p>