title: Detecting forms authentication timeout in login page
body: <p>When you have forms authentication setup to redirect to login.aspx when accessing a protected page, what's a good way to detect in login.aspx whether the user was sent there because they haven't logged on yet, or because their forms auth ticket is expired? I'd like to display a "you've timed out" message.</p>
  
  <p>(I do not mention the word session in this question, because ASP.NET treats them so distinctly, however, if there is a good solution that involves session, I'm all ears)</p>
  
  <p>I've solved this in the past by having another cooke "hasloggedin" set when a user logs in and then checks to see if that exists to determine if it's a timeout and then display an appropriate message. But, this has to be a common problem?</p>