See:

• Fix problems that cause images to not show
• http://kb.mozillazine.org/Images_or_animations_do_not_load

It is possible that you clicked "Block Images" in the right click context menu while trying to save an image. See Settings for web content, pop-ups, fonts, and languages

• A way to see which images are blocked is to click the favicon (Site Identification icon) on the left side of the location bar.
• A click on the "More Information" button will open the Security tab of the "Page Info" window (also accessible via "Tools > Page Info").
• Open the Media tab of the "Page Info" window.
• Select the first image and scroll down though the list with the Down arrow key.
• If an image in the list is grayed and there is a check-mark in the box "Block Images from..." then remove that mark to unblock the images from that domain.
• You can see the permissions for the domain in the current tab in Tools > Page Info > Permissions
• You can see all image exceptions in Tools > Options > Content: Load Images > Exceptions

Looks like this is related to the the way firefox "massages" urls. IE does not and shows all the photos properly. So, perhaps, this is a firefox problem

SEE .... https://support.mozilla.com/questions/824157