It is simply not possible to prevent someone from copying your website images. If someone is skilled and determined there's no way to stop them from abusing your website and your content. But there's still light in the end of the tunnel. You can use some semi-sophisticated techniques to limit the amount of people that can copy your website's images. Keep reading.
The first method I recommend is called digital image watermarking. A watermark can be visible or can be invisibly embedded into the pixels of an image. There are companies like Digimarc offering digital watermarking services and providing a digital identity for any media object, thus protecting it from stealing. But these systems are not fool proof, they have serious weaknesses and they are costly.
Another method would be to hide your original image behind a transparent GIF using CSS style sheets. If someone right clicks the image and selects to save it, it will only save the transparent GIF, not the original image. Similarly, you can insert the image as a table background. But in both cases a visitor can always make use of the -PrtScrn- button to copy anything from your website.
Embedding the images in Flash files is another popular method. Now, this is a neat method to use, it will make it difficult for a thief to steal your work. You cannot right click and copy the image if it's embedded in a flash file. But the flash file is already on your hard drive (cache). You can use any flash de-compiler software to easily grab any contents from a flash executable file. And of course you can simply use the -PrtScn- button to take snapshots.
You see, the truth is that there's nothing you can do to prevent a thief from stealing your content.
