ASP.NET Form Level Authentication

You can place the pages which require authentication in a subdirectory under your app's main folder. Place a second web.config in that subdirectory indicating that forms authentication is required. See http://www.theserverside.net/articles/article.tss?l=FormAuthentication for more information.

Alternatively, you can deploy all your pages to a single directory, and use <location> sections in your web.config to specify that certain pages require authentication: http://msdn.microsoft.com/library/en-us/f_and_m/html/vxconGeneralSecurity.asp