I have an ajax spinner which unfortunately has a white background in the corners. I want to remove the white and make it transparent using GIMP. How can I go about doing that? I tried opening it in GIMP and changing all the pixels to red to target but that changed the whole image when I made red transparent, and also it didn't seem to perpetuate through the sequence.
GIF doesn't have "proper" transparency. You will always have to optimize it towards the intended background. And depending on the image you might have to change every single keyframe.