How do i stop mvc pop-up login appearing by default on webpage when user is non active or not in aspnet_Users table

Question

Our application in MVC displays a prompt (windows dialogue) pop-up for username and password when user is non active or not in aspnet_Users table. I want instead to redirect to a page in the app with a message, its an internal Intranet app. I'm thinking perhaps a configuration setting somewhere as opposed to code sulution, any ideas?

thanks in advance

John