XHTML 1.0 Strict

The theme has a nested UL problem with <ul class="menu"> as the first element of <ul class="menu">. See http://d-theme.com/tapestry and hit the W3C XHTML button. Once fixed, the theme is just a few changes away from XHTML 1.0 Strict. There is a target="_blank" in your link and there is a name attribute where you could use an id. There is one inline style that could be replaced with regular CSS or you could define the default style language in head. Then you are Strict!