Firefox will load the images in the page, with two exceptions. You can prevent Firefox from loading images from certain sites, but this assumes you know in advance what sites they are. (Check out Firefox>Preferences>Content, the "Exceptions" box to the right of "Load images automatically") You can prevent Firefox from loading any images not hosted on the domain in the address bar ("third party images") but because many sites use content distribution systems, this will have a serious impact on your browsing experience. (This is a hidden preference.)

How would Firefox recognize the policy restrictions that you want to enforce? Where are they stored and how, for example, do they work in Safari?

Thank you. Indeed, this is what I meant. Not to load those third party images (the hidden preference). The previous version(s) did not load them.

Safari seems to naturally follow such restrictions. I haven't had the time to study the configuration of Safari.

There is of course that possibility of preventing automatically loading.

This article describes the hidden preference setting: http://kb.mozillazine.org/Permissions.default.image You could test that to see whether it does what you want.