There are three basic video file types on the Internet. Mpeg, AVI and Quicktime. I believe that the Quicktime file type is the most popular because many huge entertainment and news sites only use their own website.
AVI is the oldest of the three main file types. This is a Windows-oriented video format, but not the most popular because of audio and video compatibility and synchronization problems. Since Quicktime can be used on Windows or Macintosh computers, the AVI video file type is losing its popularity every day.
The mpeg format is a popular video file type that uses high output quality to increase its popularity in Quicktime format. MPEG is used for video games, cd-roms and other media that require high output quality. One of the disadvantages of MPEG is that it sacrifices the quality of the file to achieve digital quality. MPEG video files are usually large.
Another disadvantage of the mpeg format is the need for time and sophisticated hardware and software to convert simple video to mpeg. And don't forget that the MPEG format is not supported by apples and macintosh, which means that if you put MPEG video on your site, Macintosh users will not see it.
Quicktime is by far the most popular video file type developed by Apple for Macintosh users, but is compatible with IBM-compatible machines and Windows operating systems. The hardware and software needed to digitize the video is very cheap compared to the MPEG format. So it's much easier and cheaper to create a video and place it on the site with the Quicktime format.