****Update. Sheetnode 1.5 no longer requires a standalone Java Server so this post is N/A. Please see http://drupal.org/project/sheetnode for info***

The Drupal 6 theme layer gives site builders increased control of markup to customize the look and feel of their sites. Previously in Drupal, it was difficult to override system & module markup to get a truly unique design. Thanks to an improved theming system in Drupal 6, themes can now add variables, templates, and functions to completely control markup in the theme layer. Drupal 7 looks like it will offer even more control to themers. In addition, themes get the last crack at markup through overrides to gain complete control of the design.