HTML removed on saving

Configure Joomla! Text Filters

Check that your Joomla! Text Filters are configured to allow HTML. The default setting usually does, but some adjustments or re-saving the settings may be required.

Joomla! 1.5

See this article - http://docs.joomla.org/Why_does_some_HTML_get_removed_from_articles_in_version_1.5.8%3F 

Joomla! 1.7

1. In the Joomla! Article Manager, click on the Options button
2. In the Options Dialog, click on the Text Filters tab.
3. 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. 

Joomla! 2.5

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.