The template_css.css file contains the Cascading Style Sheet (CSS) used in conjunction with the index.php file, the Joomla! functions that generate xHTML code for core components, modules and plugins, and,in many cases, third-party extensions.  The subsequent text discusses CSS in the context of its role in Joomla! 1.5 .  It assumes that the reader is "CSS-Literate."  If you are not familiar with CSS and wish to learn something about it, I recommend you do a Google on "CSS" ... you will find more on this subject than you can read in a lifetime.

Joomla! 1.5, like its predecessors, has a set of default CSS classes and ids that it uses when rendering the standard views.  One significant new feature is that a "suffix" can be defined for just about every CSS class recognized by the Joomla! 1.5 core.  Joomla! 1.0.x modules have had this feature for quite a while now and in Joomla! 1.5, it has been extended to cover the general case.  Use of suffixes provides the ability to assign different styling on a per-page or per-module basis.

• Default CSS classes – this is a PDF file containing a list of CSS classes generated by the Joomla! 1.5 core
• Default CSS ids – this is a PDF file containing a list of Joomla! 1.5 CSS ids generated by the Joomla! 1.5 core

After reading the above, those familiar with the Joomla! 1.0.x series are probably thinking "Big deal, nothing new here!"  Not true!   In Joomla! 1.0.x, although it was not widely advertised, one could override the default content view.  In Joomla! 1.5, this capability has been extended to allow custom views based on individual content types (e.g., articles, newsfeeds, weblinks, etc.).  And, in doing so, one can also define custom CSS classes for use in lieu of the defaults.  And, if so inclined, replace the default table-based layout structures with div-based layouts.