The CSS / HTML Divide
I’ve been trying to ensure that you can identify the differences between Cascading Style Sheets (CSS) and Extensible Hypertext Markup Language ((x)HTML). (x)HTML organises and structures content and CSS is used to add graphical styles to the structured and marked up content.
Zen Garden Mosaic - csszengarden.com
An interesting site that illustrates this concept is the CSS Zen Garden. Many contributors modify a standard CSS file and add images to style the original HTML file.