well my problem is that I have developed a website using the new VS2012-13 it still a .NET4 platform yet it getting "The login is from an untrusted domain and cannot be used with Windows authentication", So, where is it that I can change the authentications to forms, is it somewhere in the Control Panel IIS section? Thanx.
You can do this through IIS Manager. Please read this Knowledge Base article for more information on how to connect to your site with IIS Manager. You might also want to try enabling 'Full' trust.
