For whatever reason, Mozilla has automatic image rescaling in the recent versions. Mozilla Navigator has a pref for this, but other Mozilla-based browsers, such as Mozilla Firebird, do not.

To turn it off, type in “about:config” in the URI bar in Mozilla and hit enter. After seeing a gigantic list of preferences, locate “browser.enable_automatic_image_resizing”, double click on it, and set the value to “false”. Once done, you can surf around to various places and see what the original author of the site intended.

I needed to turn it off as I view many large pictures and screenshots for work, and I want to see things at a 1:1 ratio, not some ugly-looking scaled version.