Use the Edit Anonymous Authentication Credentials dialog box to change the account that IIS uses to access your sites and applications.
UI Element List
Type the specific account name that you want IIS to use to access your site or application. By default, IIS 7 uses IUSR as the user name for anonymous access. This user name is created when you install IIS 7.
Opens the Set Credentials dialog box, where you can specify an account name and password for IIS to use for Anonymous authentication.
Application pool identity
Select Application pool identity to enable IIS processes to run using the account that is currently specified on the property page for the application pool. By default, this is the Network Service account.