You should also put this bit of text from the same site in there because I feel this is more important than disabling right click on images

It is not very secure. Anyone who understand how web pages work can easily circumvent it.
Results in different browsers can be unpredictable.
It can be annoying for visitors.

Unfortunately, watermarks are your best bet -- all other solutions can be worked around fairly easily.

I think iStockphoto handles it well -- the super-small thumbnails are too small for people to be able to rip off and use. One you go to a larger image, they add the watermark.

That just traps a right click. And I believe that web pages have no right to do this, because the mouse and browser are the property of the user, not the web designer.

If you don't want people copying your images, don't publish them on the web.