Modifying the Joomla template on your site is a breeze if you are using a template from RocketTheme.com (they have a few free ones for use as well.) This tutorial will show you how to easily change the CSS tags on your Rockettheme Joomla Template. Tools used in the tutorial are:

Gantry Template Bundle for Joomla 2.5 + 3.2 - found at:
http://www.gantry-framework.org/download

And exTplorer file manager for Joomla found at:
http://extplorer.net/files

ss editing css files in rockettheme templates