Style question - navbar width = 100%

[Darat]

I'm trying to alter the style used on a forum I admin and I want to move the navbar and make it span the whole of the page so it sits neatly under our header. However whatever I do (e.g. put it in its own <div> section with no padding) it still appears to be picking up the 25px padding the rest of the forum display uses?

How do I make it stretch across the whole of the page?

(Image attached that shows what I currently have).