How to escape page layout and set proper width?

I am working on designing myself a new site within Wordpress and I wanted to set a small white section with a bottom border that adjusts to the screen size where I could put a call to action or something. But since I am putting the div in the page, it restricts to 980px. I tried forcing it and setting a negative margin but that makes my site scroll horizontally. Is there a way to escape the page confines and scale to screen size? You can see here, its the section under the black slider section…

You have a bunch of divs set to width: 970px, and others that are 100% width. The key is not to put this special div inside one of the 970 width divs.

Your site triggers a horizontal scrollbar prematurely. This can be fixed by changing the following width value: {
    width: [COLOR="#FF0000"]860px[/COLOR];    /* from 980px */