Currently there are several known bugs in the Starlights (Akisa) web theme which is the deninet5.1 default.

Bugs for all browsers:

• "Online users" header out of style with "Who's Online" header
• Buttons and form elements are unthemed
• The top left corner of the center column can be difficult to read at times.
• The primary links menu (under the logo) moves around depending on the content type of the page being viewed.

Bugs for IE6:

• The fadout on the right side of the center column disappears when browsing the images of some galleries.
• Probably more that I haven't found yet...