IIS equivalent to Apache's .htaccess files

I'm busy trying to fight to keep the project I'm on as platform independant as possible, but it's currently a loosing battle, because the team lead insists on using Windows Domain User security, which means if you're not using IE, you can't even get to the site. I'm vaguely familiar with the .htaccess files you can use with Apache to control access, and I'm looking for a similar way to get the user's windows credentials from other browsers. Is there any way I can do this? - Theo