How is this code in FormsAuthenticationModule supposed to work?

How is this code in FormsAuthenticationModule supposed to work?

References

Reference NO 1

http://stackoverflow.com/questions/15201108/how-is-this-code-in-formsauthenticationmodule-supposed-to-work

Reference NO 2

http://stackoverflow.com/questions/11087677/prevent-formsauthenticationmodule-of-intercepting-asp-net-web-api-responses

Reference NO 3

http://msdn.microsoft.com/en-us/library/system.web.security.formsauthenticationmodule.aspx

Reference NO 4

http://haacked.com/archive/2011/10/04/prevent-forms-authentication-login-page-redirect-when-you-donrsquot-want.aspx

Reference NO 5

http://www.asp.net/web-forms/tutorials/security/introduction/an-overview-of-forms-authentication-cs

Reference NO 6

http://www.iis.net/learn/troubleshoot/security-issues/troubleshooting-forms-authentication

Reference NO 7

http://www.codeproject.com/Articles/3150/From-Custom-Authentication-to-ASP-NET-Forms-Authen

Reference NO 8

http://www.dotnetfunda.com/articles/article141.aspx