IMPORTANT NOTE: Please note that your content could be deleted by Joomla regardless of the editor unless you have correctly configured your text Filters. 

A default article filtering is imposed on all user groups. This includes the following tags: 'applet', 'body', 'bgsound', 'base', 'basefont', 'embed', 'frame', 'frameset', 'head', 'html', 'id', 'iframe', 'ilayer', 'layer', 'link', 'meta', 'name', 'object', 'script', 'style', 'title', 'xml' which could be stripped away depending upon your user privileges. You can quickly configure Joomla from stripping away your HTML tags by configuring your user groups ‘Filter Type’ to: ‘No Filtering’ or to your own preference for the respective Filter Groups.

You will find this feature in 'Global Configuration'.  Click the 'Text Filters' tab.

For more information please read Joomla’s official documentation on how to setup and configure your Article Filters:

For Joomla! 3.0 - http://docs.joomla.org/Help30:Site_Global_Configuration#Text_Filters