The ‘Lists and Libraries’ anonymous setting seems scary at first, as you may think this settting makes all of your libraries anonymously available. However, that is not the case. Each library remains secured from anonymous access until you explicitly make it available to anonymous users.
To enable Anonymous, first make sure it is enabled in the Forms based authentication zone. Via Central Administration, go to the Application Management tab and click Authentication Providers under Application Security. Change the Web Application at the top right to match the application you are enabling Anonymous Access for and then click the Extranet Zone. On the Edit Authentication page, make sure the 'Enable anonymous access' checkbox is checked. This will allow anonymous access to be set for content within this zone.
Next, log into your FBA zone and click Advanced Permissions under the Users and Permissions section on the Site Settings page. Click the Settings drop down list and then click Anonymous Access. If you do not see the Anonymous Access link, you are probably in your Windows authentication zone.
SharePoint has three different anonymous settings for site access. These settings are:
- Entire Web Site
- Lists and Libraries
- Nothing
Select Lists and Libraries. This is the minimum level of anonymous access required for pages marked anonymous to be anonymously available. As mentioned above, setting Anonymous Access to Lists and Libraries will not allow anonymous access to any content within the site unless you specifically set it for the list.
The default anonymous setting for intranet Team Sites in ‘None’.
You can read more about anonymous access by clicking the link below.
http://office.microsoft.com/en-us/help/HA101130181033.aspx?pid=CL100605171033