1. Type “about:config” (without quotes) in the browser’s address bar.
2. Type “image” (without quotes) in the Filter field.
3. Verify that “dom.disable_image_src_set” is set to FALSE.
4. Verify that “network.image.imageBehavior” is set to 0 (the default setting).
Please note that “network.image.imageBehavior” may appear as “permissions.default.image” for some browsers.