The theory behind this security model is user knows what's best for his system. In my humble opinion, this is pure hogwash (a stronger expletive came to mind but this is a family site). Is your average web surfer really knowledgeable enough to make a decision like this? Look at it this way, by installing an ActiveX control you are assuming it is secure, won't damage your system and is bug-free. You are basically trusting completely company which created control, developers and people distributing image.

Yes there are security certificates involved, but those are relatively easy to get. Also remember how many security problems have been reported involving ActiveX controls.

Due to limited number of colors, GIF is primarily useful in images with a distinct separation of colors. A cartoon, for example, is ideal for GIF format.

When you save an image in GIF format, you have option to specify how many colors will be saved. By doing this you can decrease size of an image even further. All of tools which are available to optimize GIF images work by reducing number of colors to bare minimum. This can produce astounding results in size of finished file.

Unlike JPEG, GIF uses a non-lossy compression algorithm. This means that images do not loose bits when they are decompressed. In order to accomplish this, GIF uses a proprietary encoding/decoding scheme called LZW (Lempel Zev Welch). LZW is an excellent compression algorithm which typically results in very small files (in comparison to fully expanded BMP files).