IIS ASP.NET authentication error

Login failed. The login is from an untrusted domain and cannot be used with Windows authentication.

If this error occurs in SQL Server login using windows authentication when accessing your web page using IIS, then verify the login in the application pool and make sure the access is working. 

When the domain password is changed that IIS application pool is using, then application pool identity needs to be set.

Thanks 

Gokulnath