APNG Images
Some of the emotes used on Multiverse, as well as some users avatars and signatures, use the APNG image format. Many browsers do not support APNG natively, and will display a static PNG instead of an animated one.

Those using Internet Explorer or Safari should switch to another browser, as they don't support APNG at all.

Chrome and Opera need a plugin:
Chrome Plugin
Opera Plugin

Firefox supports APNG natively.