Support 1366 * 768 in a 1920 * 1080 based site

I am working on revamp a site that would like support 1366 *768

In 1920 * 1080 , it works fine. However , when I try to visit the site on macbook air (1366 * 768), part of the site has cut. But I have not fixed the height of the site before

The structure is #nav_bar at the left side , and #content for the right side, and the footer is position:fixed

This is not a responsive site, so it does not matter if I can scroll / resize the whole site for smaller screen

In short, which element should I adjust so I can view all content just the same as when I visit in 1920px screen e.g. body? thanks

The site:

http://ift.tt/1S2M5Tv