if user sign off w/o loggin goff then the logoff with occurs when the session ends. Look at your global.asax ->

Sub Session_End(ByVal sender As Object, ByVal e As EventArgs)
Application.Lock()
Dim UserSession As ArrayList = Application("UserSession")
Dim NamePassword As ArrayList = Application("NamePassword")
Dim who As Integer = UserSession.IndexOf(Session.SessionID)
UserSession.RemoveAt(who)
NamePassword.RemoveAt(who)
Application("UserSession") = UserSession
Application("NamePassword") = NamePassword
Application.UnLock()
End Sub


FK