We have a detailed answer on our forum GetSatisfaction - How do I stop people right-clicking and saving Images - http://getsatisfaction.com/SynthaSite...
The good news however, is that there are other ways to protect your pictures, and make sure that you get suitable credit where credit is due:
1) Watermark the images:
This is the most effective way to ensure that another user cannot take your pictures and use them as their own - and what is better, if they do take the pictures and use them on their own website, they will effectively be advertising your work for you for free. If you are selling your work; what many people do is provide low-resolution watermarked images on the site, with an order form for people to request the larger unmarked images.
2) Publish your pictures under a license:
Creative commons provides an easy way for you to choose a license for your work. Check out their license generator: Creative Commons - http://creativecommons.org/license/
Kershnee is right... put a water mark on your photos. Here is where you need to go for real copyright protection http://www.copyright.gov/
If you register your work as a collection ...It is much cheaper that way.Still do the water mark as most 12 year old's on the net can get around anything you can come up with to try to stop downloading your work.