Michael Jervis shares another gem from his former employer (the place with the custom in-house "development" "tool"). At first glance, if may seem like a runner-up in the Nested-If competition. But it's far worse than that ... 

Set WSObj = Server.CreateObject("WScript.Network")
If sUserName <> "" Then
  If CheckLicences(sUserName) Then
    If Not(CheckLogonOther(sUserName, WSObj.ComputerName)) Then
      If AccountExist(sUserName) Then
        If CheckDisabled(sUserName) Then
          If CheckPassword(sUserName, sPassword) Then
            If Not(CheckPasswordExpDate(sUserName, sPassword)) Then
              If Not(CheckPasswordExpSoon(sUserName)) Then
                If Not(CheckFirstLogin(sUserName)) Then
                  Call SetupSessionVars()
                  Call AddToUserTable(sUserName, cstr(sClientIP), "page.asp")
                  Response.Redirect("../pages/page.asp")
                Else
                  Call SetupSessionVars()
                  Call AddToUserTable(sUserName, cstr(sClientIP), "ChangePassword.asp")
                  Response.Redirect("ChangePassword.asp?ChangeMode=FirstLog")
                End if
              Else
                Call SetupSessionVars()
                Call AddToUserTable(sUserName, cstr(sClientIP), "otherpage.asp")
                Response.Redirect("../pages/page.asp?DaysLeft=" + cstr(NumberOfDaysLeft(sUserName)))
              End if
            Else
              Call SetupSessionVars()
              Call AddToUserTable(sUserName, cstr(sClientIP), "ChangePassword.asp")
              Response.Redirect("ChangePassword.asp?ChangeMode=Expiry")
            End if
          Else
            Session("Attempts") = Session("Attempts") + 1
            If Session("Attempts") >= 3 Then
              Session("Attempts") = 0
              Call DisableAccount(sUserName)
              Response.Redirect("login.asp?Err=2")
            Else
              Response.Redirect("login.asp?Err=1")
            End if
          End if
        Else
          Response.Redirect("login.asp?Err=3")
        End if
      Else
        Response.Redirect("login.asp?Err=1")
      End if
    Else
      Response.Redirect("login.asp?Err=5")
    End if
  Else
    Response.Redirect("login.asp?Err=6")
  End if
Else
  Response.Redirect("login.asp?Err=1")
End If

Each function call (AccountExist, CheckLicences, etc) creates a related COM object (clsAccountExist, clsCheckLicences, etc) and calls the corresponding method on that object (AccountExist, CheckLicences, etc). The method on that object in turn creates a COM object (clsAccountExistDA, clsCheckLicencesDA, etc) that abstracts the database access (clsAccountExistCRUD, clsCheckLicencesCRUD, etc) which finally calls a stored procedure in the database. Phew!

Now you may be thinking gee, with all those layers, it must be good. And yes, although it really pains me to say, a Windows-DNA architecture ... can ... be ... ... ... good ... sometimes. But if your object-oriented solution is a class for each function you need, I'm not sure any enterprise architecture pattern will help ...

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