How can I change the middle, or actually all three columns--middle, left side boxes, right side boxes--to 60%, 20%, 20% respectively? Essentially, I want to get rid of all the excess white space for persons viewing my pages with a larger screen size.

Also, some of my manufacturing logos are too big and do not display correctly on individual product pages. For reference, please see:

www.custom-builtpc.com

Thank you in advance for any advice you provide.

Sincerely,

William