Use ASP.NET Impersonation authentication when you want to run your ASP.NET application under a security context different from the default.
If you enable impersonation for an ASP.NET application, that application can run in one of two different contexts: either as the user authenticated by IIS or as an arbitrary account that you set up. For example, if you were using Anonymous authentication and chose to run the ASP.NET application as the authenticated user, the application would run under an account set up for anonymous users (typically, IUSR). Likewise, if you chose to run the application under an arbitrary account, it would run under whatever security context was set up for that account.
UI Element List
The following tables describe the UI elements that are available on the feature page and in the Actions pane.
Feature Page Elements
Select to manage ASP.NET Impersonation authentication.
Actions Pane Elements
Turns on ASP.NET Impersonation authentication.
Turns off ASP.NET Impersonation authentication.
Opens the Edit ASP.NET Impersonation Settings dialog box where you can specify the identity under which the ASP.NET application should run. You can perform this action only when you select ASP.NET Impersonation from the list on the feature page.