This option specifies that that your Web site will use ASP.NET forms authentication, which relies on the ASP.NET membership system. When you use forms authentication, users log in to the Web site by using the login page that you created earlier in this walkthrough. (The from a local area network option configures the web site to use Windows authentication, which is practical if your site is accessed only by people who are on a corporate network. As noted earlier, this is the default setting for ASP.NET membership.)