Zencoder
Zencoder is the creator of an open-source HTML5 video player, Video.js, built with Javascript, HTML, and CSS. Video.js plays video via native playback in all HTML5 browsers and devices, or through Adobe Flash when HTML5 playback is not available.
HTML
The Document Type Declaration is for HTML5. If a declaration is not included, various browsers will revert to "quirks mode" for rendering.