If you receive the message:

This message appears ( 403 forbidden ) this page can only be accessed by authorized users only.  When trying to access pages on your web site.

This may be because:

You may restrict access to pages so you must login through the "Subscription" page type.  Some times users accidentially restrict pages even though they are not using the Subscription feature.

Resolution:

Go to the page settings of the forbidden page and UNCHECK the "Restricted Access" checkbox.  Save and Publish the page.  SEE VIDEO BELOW