Table <Tablename> is marked for deletion and was not added to the diagram. (Visual Database Tools)
A table that has been removed from the diagram will be deleted from the diagram when the changes are saved. The table will not, however, be deleted from the database.
For more information, see How to: Remove Tables from Database Diagrams (Visual Database Tools).
The table has been deleted from the database by another user and cannot be added to your diagram. For more information, see How to: Delete Tables from a Database (Visual Database Tools).