My entire site, including all the puzzles, is protected by international copyright under the Berne Convention of 1971. Nothing needs to be marked as protected — everything published on the internet is automatically copyrighted at publication.
You may view the material on this website in a browser for personal, non-commercial use only. Electronic storage of the material is not permitted. You may not sell or modify any of the material, or reproduce, display, distribute or otherwise use it without my written permission.
And since some believe sudoku puzzles are not copyrighted, I recommend reading 10 Big Myths about copyright explained.