About anonymous access (Windows SharePoint Services)
Applies To: Windows SharePoint Services 3.0
If you enable anonymous access when you create a Web application (see Create or extend a Web application (Windows SharePoint Services) for more information about creating Web applications), you can control anonymous access to site collections within that Web application both at the Web application level and at the site collection level. If you do not enable anonymous access when you create a Web application, you cannot enable anonymous access at any level.
If you disable anonymous access at the Web application level, it is disabled for all site collections within that Web application and cannot be enabled at the site collection level. If you enable anonymous access at the Web application level, it can be enabled or disabled at the site collection level (for more information, see Configure authentication providers (Windows SharePoint Services)).