Testing this theme athttp://d-theme.com/colorart. W3C accepts the XHTML as XHTML 1.0 Strict. The more detailed Total Validator picks up two errors. The following lines have style attributes and the default style sheet language is not specified. The best solution is to change the styles to CSS classes.

<div id="mainContent" style="width: 860px;">
<div id="sideBars" style="width: -10px;">