First make sure your WYSIWYG editor is set to none in your global configuration area. If this doesn't work then also note the editor parameters are important to check, however 1.6 also uses a new Text Filter parameter on the content manager for both article content and modules. If you want an article or module to display html tags, you need to alter the parameter for your user group. Content > Article Manager > Options (Toolbar button) > Text Filters (Tab) Set Super Users to "No Filtering".
In Joomla 2.5+ the content filter has been moved to the Global Configuration area.