Main Navigation Width

Hi There,

Is there a way to change the width of the mail navigation bar? I have entered this code in my child theme and nothing happens.

.main-navigation {960px x 0px;}

Also, how do I change the width of the side bar widget area?

Basically I want the entire width of the site changed to 960px (main nav tabs, content area, footer)

Please help, Thank You!
http://kneesecustomhomes.com/