Asp.net WebPage with Active Directory Group Authentication

[rsk]

I have 2 pages Authentication.aspx and Default.aspxIn my authentication.aspx page load event I make sure the user is part of a particular group in Active Directory if not it redirects them to an error page which seems to be working. Then if they are part of the correct group it redirects them to the Default.aspx.Code for pageload event of Authentication.aspx\[code\]protected void Page_Load(object sender, EventArgs e){ PrincipalContext pCTX = new PrincipalContext(ContextType.Domain); UserPrincipal user = UserPrincipal.Current; GroupValidator groupValidate = new GroupValidator(); if (Request.IsAuthenticated) { //lblInfo.Text = "<b>Name: </b>" + User.Identity.Name; //lblInfo.Text += "<br><b>Authenticated With: </b>"; //lblInfo.Text += User.Identity.AuthenticationType; if (gv.IsUserInSetup("GroupName", user)) { Response.Redirect("Default.aspx"); } else { lblInfo.Text = "Could Not Authenticate User Please Try Again!"; } } else { lblInfo.Text = "<b>Name: </b>" + "Could Not Resolve Name!"; }}\[/code\]But if I type \[code\]http://localhost/Default.aspx\[/code\] directly it by passes the authentication page and loads the default page. How can I prevent a user from typing in this page directly and make sure that they come from the Authenitcation.aspx page?