Hi Gary,
For the restricted areas you will see that the template often uses a div class called rt-container to wrap around other divs or to sit inside the full width divs.
For example if we look at afterburner2 template we can see the following source code in he browser...
<div id="rt-top">
<div class="rt-container">
<div class="rt-grid-12 rt-alpha rt-omega">
When viewed on a desktop we see the following css is assigned...
#rt-top-surround {
color: #C7C7C7;
}
.rt-container {
margin: 0 auto;
position: relative;
width: 1200px;
}
.rt-grid-12 {
width: 1200px;
}
These are the basic css elements and there are other pieces of css for styling that I haven't included here.
As you can see, there is no width for the rt-top-surround div so it will fill the screen.
The div class rt-container is set to be relative in position to the other divs and to have a width of 1200px. The margin is set for 0 top and bottom and auto for the sides, which will centre it on the screen.
Inside the container would be your selected layouts e.g. 1 published item = 12 grid etc. In this example the rt-grid-12 is set to 1200px width. If you published 2 positions with the 6|6 setup then they would be 600px each.
Hope this helps