By default Liferay 6.1 does not check if guest has view permission on content in public sites. This is so for performance reasons based on the assumption all content in public site is ... well ... public. If you want to change that, you need to set journal.article.view.permission.check.enabled
to true
in portal_ext.properties
With that change in place, you can go to Control Panel -> Roles -> Guest Role -> Define permissions
and set the default permissions for Web Content
resource
Speaking of permissions in 6.1, you may find this post useful.