Firefox has stopped displaying a lot of graphical content. It varies between sites, and I can't see the logic of it. For example, on Huffington Post, advertising images appear, pictures for articles do not. On Flickr, my pictures are visible, icons are not. Amazon has ad images, but no images of products. New York Times displays everything. The option for "Load images automatically" is checked. I tried reinstalling. Sites appear correctly on other browsers. Any ideas?