Is GIF the only major image format that supports animation?
With GIF images being a relatively poor quality format, why are they the only one that supports animation in most viewers / browsers?
There is a format of PNG out, APNG, that does what GIF does but better. It is still not supported in all browsers, but it is on the rise.
Since the libpng(used by blink in chrome/opera/chromium) committee has locked up, and as it does not seem like any changes will come soon, a better choice might be to use Video with alpha-channel.
Shown here: Video transparency Example
Animated GIF remains widely used, as many applications are capable of creating the files, and it remains the only animation format supported in nearly all modern web browsers without the use of a plug-in.
There are other animation formats like for example MNG (http://en.wikipedia.org/wiki/Multiple-image_Network_Graphics). Embedded Adobe Flash objects, MPEG, WebM, and other video formats can be used in place of animated GIF in many websites.