De aqui
No Mozilla Suite e no Firefox:
- Na barra de localização, digite about: config e pressione Enter
- Digite "anim" no campo Filtro (para encontrar rapidamente a preferência necessária)
-
Clique duas vezes na linha image.animation_mode e edite-a para um dos seguintes:
none — will prevent image animation
once — will let the image animate once
normal (default) — will allow it to play over and over
(ou)
For Mozilla Suite/SeaMonkey, under "Privacy & Security -> Images", make sure that "Accept all images" is selected.
Also, under "Advanced -> Scripts & Plugins", make sure that "Enable JavaScript for" "Navigator" (or "Browser") is checked and make sure that, under "Allow scripts to:", a checkmark is included next to "Change images".