Artemiss is a quick-and-easy app to download images from the web. No need for installing any other software or plugins. It supports almost any site you can imagine. The best thing is that you don't need to deal with any popups and other ads. Just hit Alt + A to download all images.

To be able to download an image, it has to contain an image. To find out if a URL contains an image, just go to the URL in a web browser and see if it displays an image.