ASP.NET can only have one loginUrl. All unauthenticated users must go through this single page. But from this page you can redirect the user to the "real" login page, using returnUrl from the querystring to find out to wich page to redirect.
I used this solution a couple of years ago on EPi 4.61. The returnUrl contained the page id. I used the page id to know wich login page that should be used.
I solved this using a different aproach. I've explained my solution in the blog post "Authenticate users from different sources" at http://epinova.no/no/Blog/episerver_blog/
Lars Øyvind Bodahl
We have made a loginpage for extranetusers, and set the path in web.config
<forms name=".EPiServerLogin" loginUrl="/Logg-deg-inn" timeout="120" />
This works fine, but the Webeditors/webadmins also get redirected, and we want them to go to the episerver loginpage.
We have set the Episerverlogin to go to: http://<episerversite>/Login/ in the sitesettings in web.config.
How can we solve this?