Plugins
Get flash to fully experience Pearltrees
html5.org — HTML revisited
HTML5 is the latest version of HTML and XHTML. The HTML standard defines a single language that can be written in HTML and XML. It attempts to solve issues found in previous iterations of HTML and addresses the needs of Web Applications, an area previously not adequately covered by HTML.
MediaElement.js - HTML5 Video & Audio Player « WordPress Plugins
Video and audio plugin for WordPress built on the MediaElement.js HTML5 media player library. Provides Flash or Silverlight fallback players for non-HTML5 browsers. Supports iPhone, iPad, and Andriod.
bo:VideoJS - HTML5 Video Player for Joomla
In order to watch a video you need to have a current browser version. But not every current browser version will be able to support every video format (e.g. for licensing reasons): Here you will find a detailed overview explaining which browser supports which format: http://camendesign.co.uk/code/video_for_everybody/test.html . The player contains a fallback-option (to Flash), in case the target browser cannot display HTML5 formats. More information regarding fallback: