Configure Joomla! Article Filters

By default Joomla!  'cleans' content on saving, removing video code elements such as object, embed, video, audio and iframe.

A simple article parameter change is all that is required to fix this.

Joomla! 1.5

See this article - 

Joomla! 2.5 & Joomla 3

  1. In the Joomla! Global Configuration, click on the Text Filters tab.
  2. For the Super Users group, or any other trusted user group, set Filter Type to No Filtering. Make sure that you only set this option for user groups that can be trusted as setting the Filter Type to No Filtering will essentially allow the user to include any html in an article.