AddUser Directory Configuration File (Web.config)
You should set up the Web.config file to have the following entries and place it in the AddUser directory (containing AddUser.aspx). These settings allow anyone to view the AddUser.aspx page.
<configuration>
<system.web>
<authorization>
<allow users="*"/>
</authorization>
</system.web >
</configuration>
See Also
ASP.NET Web Application Security | Forms Authentication Using an XML Users File