you can make access to different pages by using Session.

every user has its own role. so in database define Roles for every user.

like
there would be three fields ..

User name , Password and Role.

when you click on the button sign in
if the username and password matched.

put the respective role in the session variable like that.

like .... Session["Role"] = "Admin";

now check in every page_load event of every page.

like

Page_Load()
{

if(Session["Role"].ToString() != "Admin")
{
Response.Redirect("Login.aspx");
}
// same thing u can use for every user role
}

Thanks for your reply. Let me try with this and get back to you.