If you try to configure an IIS site to use integrated security and still get the prompt for credentials, here are few key things to validate.
First, make sure that Anonymous Authentication is turned OFF for the site:
Second, enable integrated security in Interner Explorer (Options/Advanced and checkin the “Enable Integrated Windows Authentication” option).
Third, add your website to Local Intranet zone and select at least “Automatic logon only in Intranet Zone” option under Options/Security Settings/Local intranet/Custom level).
Fourth, make sure the user and application server are in the same domain.