Ccreating boxed post/page area?

Hi all

I’d like my blog to have a narrower body than the width of the screen. Johnny Tuch has helped me with the following solution:

.tc-header{
max-width: 1170px;
margin: 0 auto;
}

footer#footer {
max-width: 1170px;
margin: 0 auto;
}

However, I just realised that the area under the slider is not boxed. Therefore I cannot have a different colour for the general website background and the page/post area background. Any Idea How to achieve that?