There are settings in your profile that prohibit someone downloading, as well as disabling the right click 'save picture' option. This message appears when viewing your image with the download option set.
Download The owner has disabled downloading of their photos
But anyone can do a screen grab and then crop out everything but the image, but it will take some effort and won't be of very good quality.
Also, the "no right click to download" thing is easily defeated. If you're concerned about someone taking your photos, you ought to watermark them somehow.