Anonymous access is the permission that every user can enable to log on to sites without having credentials.

Follow the steps below to enable anonymous access:
  1. Central Administration->under Application Management->click on Manage web applications.
  2. Make sure you select the site you want to enable anonymous access on. Click on the Authentication Providers icon.
  3. On the Authentication Providers pop-up window click on the Default zone.
  4. Under Edit Authentication, check Enable anonymous access and click Save.
  5. Going back to Web Application Management, click on the Anonymous Policy icon.
  6. Under Anonymous Access Restrictions, select your Zone and set the Permissions to None – No policy and click Save.
  7. Now, the web application will allow anonymous access set. So, navigate to your top level site collection for the web application. Click Site Actions > Site Settings. Under Users and Permissions click Site permissions.
  8. Under Permission Tools, click the Anonymous Access icon and set the permissions to Entire Web site and click OK.

If you followed these steps properly you should now have Anonymous Access enabled.

- See more at: http://expertsharepoint.blogspot.de/2014/05/how-to-enable-anonymous-access-to.html

Note: If you find a different solution, please report it as a comment to this post. This will be useful to the SharePoint Community. Be sure to double-verify it: undo your solution and verify that the problem comes back, then redo it and verify that the problem goes away.

See Also

  1. SharePoint Resources on the TechNet Wiki
  2. SharePoint 2013 Portal
  3. SharePoint 2013 - Service Applications
  4. SharePoint 2013 - Resources for Developers
  5. SharePoint 2013 - Resources for IT Pros