Remove page margins or make them transparent

Hi, this is the site I’m working on: https://www.garywoodill.com/

I’m trying to use a background image to extend the header area beyond the sides of the page. The problem is the margins of the page block part of the background, leaving white bars. I’d like to get rid of the left and right page margins so that the background image connects with the header area or simply make the page transparent.

If it helps, here is a link to the CSS: https://www.garywoodill.com/wp-content/themes/twentyten-weaver/style.css

I’d appreciate any help, thanks