Template editor isn't very friendly at the moment.
Change the word 'template' to something else... 'theme' ?
User is forced to write styles directly into XSL template. Need to provide the ability to create CSS files seperately in the editor.
 
Probably use a tree list view, 2 levels:

• Blue Theme
• Red Theme
  ---- theme.xsl
  ---- theme.css
• Yellow Theme
   
  Join the editor window and the preview window into a single tabbed window.