Before HTML5, browsers were not able to play video natively (that is, without the use of a plugin that must be installed and does not come with the browser). It has been common place to use Flash to deliver video content; typically with videos encoded in FLV format and played through some kind of SWF player. Although this serves its purpose, it’s still not native; users have to have the flash playback component installed in their browser to playback the content.
This post will just focus on the loop attribute. I’ll be explaining browser support of video formats in another post soon.