There is no 100% way to protect your images from taken in the internet. The 100% way is not to display it in the internet. You can prevent a novice visitor, but for expert visitor it is no use, because there will ALWAYS be a way to get any image. But anyway, here is how you can prevent your image being taken:

• Use a watermark. Put a mark that could show the real owner of the image but still look nice visually for the common visitor. You can do this with an image software.
• Using CSS. The idea is to a transparant image above the real image, so when the user right click to save the image, he is saving the transparant image. Here is the code:

<img src="realimage.gif" width="200" height="100"> 

<img src="transparent.gif" width="200" height="100" 

style="position:relative; left:-201px; top:0px;">