UGTS Document #76 - Last Modified: 8/29/2015 3:23 PM
Forms Based Authentication with ASP.NET
Forms Based Authentication (FBA) allows a website to require logins for users (thereby identifying them), with whatever user interface and whatever authentication method the website chooses to use.
There are some limitations to FBA. You can't have two different authentication systems for the same web application. In other words you can't have Integrated Windows authentication on one subfolder and FBA on a separate subfolder, unless those subfolders are handled by separate applications. And since FBA has some application wide settings, such as the URL for the login form, an application can only have one login form page.
In practice, neither of these are really limitations because FBA can include Integrated Windows Authentication internally through a Server.Transfer. Likewise, a Server.Transfer can be used to selectively choose one style for a login form vs. another based on the ReturnURL query parameter.