ROLE BASED LOGIN AND REDIRECT

Creating a website in which i want to create a role based userlogin like admin and user and redirect the user based based upon role to admin and user page respectively and add security options as well.
i hve two folders admin and member and their respective web.config files.But in my main web.config file whenever i want to add authentication and authorization it does not work.All the pages in my website shows error such as GUI is lost.What possibly wrong am I doing?