Use Fiddler to Debug An ASP.NET Page

If you are using Windows Server 2008 you won't be able to view HTTP response/requests while working with ASP.NET applications that are hosted on LocalHost. To be able to monitor the request/responses that are initiating from your local machine include a "." after the localhost so Instead

http://localhost:4303/Default.aspx

try

http://localhost.:4303/Default.aspx

There is also one option in Fiddler which can cause problems and has to be turned off So in Fiddler goto Tools --> Fiddler Options -->General Tab --> Uncheck "Enable IPv6 (if available)"