flickr gives users the ability to protect files from being downloaded. If you try to download a file that is protected on flickr, you end up with an image called spaceball.gif that is not the image you wanted. But if you really want to download a protected image from flickr, it's very easy to do if you are using Firefox.

Just right-click somewhere on the page and select View Page Info from the menu. When the Page Info panel opens, select the Media tab. In the upper section, every image on the page will be listed. You can scroll through the images and they will shown in the lower section of the panel. Once you find the image you want, hit the Save As... button right above the image viewing area and you will have a download of the protected flikr image.