webform password protected page

Hi all,
I am new for using C# to develop web app.
I made a web project which was password protected by using form mode
authentication.
in my login page ,I added one button of "add a user" which linked the
page to add a user to database. I confronted one problem.
now whenever a user click "add a user" button, it won't go to the
linker,it always stay in the login page. I guess it is my web config
problem which always try to authenticate my role.
anybody there has idea about this web config?
thanks

.