When I try to delete some page(s) from the Manage Pages window, this notification appears in the popup: 

    "Page Name" - This page is referenced from some object(s) as follows:
    * Navigation (Admin View)
    * Navigation (Normal View)
    This page is not allowed to be deleted.
    First delete the object (or change its link reference) and publish the page where the delete was made.

This message means there are still references to this page, and to help prevent broken links on the site, the references  must be deleted before the page can be. If you are unable to find the links in the obvious areas, the links may be part of a hidden secondary navigation, or another hidden element. In this case, the element needs to be re-enabled, adjusted, and published to delete the pages.