I have an site collection in a web application for which I need to enable forms based authentication (rather than using the standard Windows/AD authentication).
I followed the rather good instructions at http://donalconlon.wordpress.com/2010/02/23/configuring-forms-base-authentication-for-sharepoint-2010-using-iis7/ and confirmed that the web.config files are properly setup after having gone through this procedure.
The problem I have is that I do not get a authentication login web page when going to any of the sites in the collection - I should get a drop-down asking if I want to use forms-based or windows-based authentication. Instead I get a straight web-browser pop-up username/password dialogue. Furthermore, I cannot login using this dialogue.
Creating a new web application and new site collection within does give the expected web page with the choice of authentication method, and I can log in there using the forms-based user.
So what's the magic for enabling this on an existing web application/site collection?