I am a photographer on the side so I can relate to your need to protect copyrighted photos. What we do is create a new layer in photoshop and type out what you want for a 'watermark'. (usually just the © and our studio name) Then you can change the opacity of the layer to make it light but still readable. You won't be able to fully protect any image on a website. Even disabling the right-click function is by-passable.