Categories Bar

Hi I was hoping to get some help. My site is GahhModels.com and I want the menu bar to stretch as big as the browser window. It stops for the width of my page template but I want the Bar part to go beyond, but of coarse keep the home, models etc buttons to stay as is.

Im using the mystique theme.

Also Id like my categories “Home, Models etc” to be spread evenly of the pages width and when/if new categories are made it would adjust corectly.

Thanks in advance. This is my first site doin anthing and so far so forgive me for any noob questions and what not in the future 😛