Stark has minimal CSS to let you see the effects of the CSS added by Drupal and add on modules.

Download Stark from drupal.org/project/stark. This version is 6.x-1.0 from 2009-Jan-31, a 17.55 KB download.

The W3C validate the CSS at levels 2.1 and 3. The HTML fails with just one error. There should not be any white space at the start or end of an attribute's value. This error is common to many themes and makes automated validation reject the theme.
<div id="navigation" class="menu withprimary withsecondary ">

Wave did not detect accessibility errors. Cynthia Says this theme is US 508 and WAI compliant as far as a computer can check.