When I enable basic authentication for my Orchard website then styles/images/js files get redirected to the forms authentication login URL (ex: "/styles/login.css" is redirected to "/AccessDenied?ReturnUrl=/styles/login.css").
I'm using IIS 8.5 on Windows Server 2012. I already installed the Static Content feature for IIS. The user I'm using for basic authentication is an administrator and has full permissions to all of the Orchard files. I added <allow users="*" /> to the web.config in the appropriate directories but that made no difference.