How to enable Anonymous access in SharePoint 2010
Go to central admin site
In Application management click on Manage web applications
Select the web application and click the Authentication Providers in the ribbon.
In Authentication Providers click on Default link
In Edit authentication, enable the Anonymous access.
After you click save, the web application will allow Anonymous access to be set, but you have to set this from the actual web application also.
Navigate to the top level site collection for the web application and click Site Actions > Site Settings > Site Permissions. From that menu you can click Anonymous Access:
From there select Entire Web Site and click OK: