I've used Atahualpa for loads of sites and have always used the following code to remove the dashed line round the page-center and cat-center menus:
However, I'm working on a site today and it just isn't working! Wondered if you could help at all. Site link is http://22.214.171.124/aliwp1.co.uk/
On this site I've added the grey image via the Header Overlay box and also need the menu bar to be transparent so the image is over the menu option when there are more things in there.
I'm using WP 3.3.2 and Atahualpa 3.7.6