there are many types of AVI compressors or codecs which look like an extension icon quicktime has a few preinstalled but different companies keep making more to improve compression and therefore playback. one that I know of is dvix, but I had trouble installing it. (I don't really bother trying to watch online movies anymore because I have 56k and they generally take forever to download) I only know this because a site I was on once had a note next to a clip that I would need this codec. you should try contacting site admins to see what codecs they are using.