Different settings in the config file effects the behavior of an ASP.NET application, and those files are:

• machine.config
• web.config

The machine.config file contains default and the machine-specific value for all supported settings. All things pertaining to the settings of the resources hardware will be contained in this file.

An application override the definition of the settings done by the machine config file.The web.config file is a subset of the machine.config file.

If the application contains child directories, it can define a web.config file for each folder.

Any web.config file can locally extend, restrict, or override any settings defined on the upper level.

A default web.config file is generated as default by Visual Studio. Here without any web.config file an action can be executed by an application, however application can be debugged without a web.config file.

For example

// This will show the look of configuration file
<configuration>

   <!-- Configuration section-handler declaration area. -->
      <configSections>
         <section name="section1" type="section1Handler" />
         <section name="section2" type="section2Handler" />
      </configSections>
   <!-- Configuration section settings area. -->

   <section1>
      <s1Setting1 attribute1="attr1" />
   </section1>

   <section2>
      <s2Setting1 attribute1="attr1" />
   </section2>

   <system.web>
      <authentication mode="Windows" />
   </system.web>

</configuration>