The link above is an excellent in-depth article to HTML5 which explores the creation of files for HTML, and how to properly use the <video> element in HTML5 with your newly created content. A great excerpt for use with encoding.com:
“As you can tell, video (and audio) is a complicated subject — and this was the abridged version! I’m sure you’re wondering how all of this relates to HTML5. Well, HTML5 includes a <video> element for embedding video into a web page. There are no restrictions on the video codec, audio codec, or container format you can use for your video. One <video> element can link to multiple video files, and the browser will choose the first video file it can actually play. It is up to you to know which browsers support which containers and codecs.”
This brings up the discussion over why encoding.com is such a useful tool: the ability to deliver those formats as needed to the client web server and get video support for all of the browsers. Here's a list of the containers which will likely be commonly seen in HTML5: MP4, OGV, FLV, WEBM, AVI. All of these are available via encoding.com (or will be shortly as of the writing of this article, with WEBM and OGV almost in beta), and will give the ability for deliver to all the major browsers supporting HTML5.