Some web sites disable the right-click functionality on their web pages so that you can't right-click to download the images off their site. Annoying to be sure. But also a futile effort.

If you are on a web page where you want to download one of their images and they have disabled the right-click on the mouse, do this instead: left click on the image and hold the mouse button down. While still holding the left mouse button down, drag the mouse to your desktop and let the button up. Ta-da! The image will have been dragged to your desktop and you have downloaded this image even though right-click was disabled.