Nice work....good to see a div based layout at work in a dnn site. A couple of friendly observations:
The horizontal menu doesn't render properly in IE 7. It may be a margin, width, or padding issue in the menu's css as I believe FF and IE handle these differently.
In FF, you can remove the accessibility border around your menu items with this
:focus
{
-moz-outline-style: none; /*remove accessibilty border */
}
Paul