The settings that are managed through the Application Settings feature of the Application tab exist in the section of the ...

The settings that are managed through the Application Settings feature of the Application tab exist in the <appSettings> section of the Web.config file for the Web application. This is a predefined configuration section provided by the .NET Framework. The highlighted lines in the following code are an example configuration file that is generated after you use the Web Site Administration Tool to create an application setting named ApplicationName.