Elements in a web.config File

<configuration> In a Web.config file, all the configuration information for an ASP.NET application must reside between the <configuration> and </configuration> tags. This is the root node, which contains the declaration of all other sections of the Web.config file. <appSettings> This section of the Web.config file provides a way to define custom application settings for an application. The section can have multiple <add> subelements. <appSettings> <add key="connectionstring" value="localhost;uid=readonly;pwd=user"/> </appSettings> <compilation> This element sets several compilation settings for the application. Some of the settings involve setting a default language and debug option for the application setting. Debug pages are larger and execute more slowly, so you should use them only for testing purposes. This section also provides support for the <compilers>, <assemblies> , and <namespaces> subelements. <namespaces> This subelement is used to add or remove namespace references for assemblies that must be made available when compiling Web pages. <authentication> The <authentication> element sets the authentication policy for the application. Possible modes are "Windows," "Forms," "Passport," and "None." <pages> The <pages> element allows configuration of page application specific settings. <customErrors> The <customErrors> element provides a means for defining custom error messages for an ASP.NET application. This is generally used to point users to a friendlier message than the default error messages. The <customErrors> element section supports multiple <error> subelements that are used to define custom errors.