As Ethel says, it's impossible to protect pictures on a website. There are various ways which, to the novice user, appear to disable the ability to save a picture to a hard drive but all that anyone has to do, to overcome this, is to save the entire web page and then look through the files which make up that page and find the picture.
Yes, it's a breach of copyright but you can't stop it and (because, in most cases, you'd never know that it had happened) you can't take action against anyone who does so.
The best techniques to protect saleable images are to use small low-resolution pictures (which won't print well) on your website and/or to add a watermark to your pictures.
For example, look at these photos offered for sale by Getty Images:
http://www.gettyimages.com/Search/Search.aspx? src=quick&contractUrl=1&family=editorial&phras e=new%20york#
Pictures taken directly from that page are too small to be useful to most people. To see a much larger picture, you simply have to click on the required image. However, the picture you'll see will have a prominent watermark added. You can't get the 'proper' picture without payment.
Chris