Upload the video to Vimeo or YouTube, let them do the hard work.
Okay, so you want to host it yourself. Convert the video to MP4/H.264/AAC format using Handbrake or
ffmpeg, then embed a Flowplayer player into your webpage. If MP4 doesn't work, try FLV. (YouTube serves both of these formats.)
If you want to avoid Flash, most popular browsers now implement the HTML5
<video> tag, which allows embedding videos directly. Unfortunately, the codec support is a very big mess of patents and ideologies, and those who choose to use
<video> have to resort to publishing several different formats including a Flash-based player.