What they use is based on the same principle as I gave you:

.left {
    float:left;
    width:120px;
}
.right {
    float:right;
    width: 100%;
    margin-right: -120px;
}

Note: this is useless as it's what CSS box layout does by default:

    float:right;
    width: 100%;

Reading this helped me a lot understanding how all this formatting goes; takes less time reading than all the trial and error process you go for finding the right CSS

Back to your problem, I don't think the CSS box model allows what you're looking at; you'll probably will need some JS to do this.

>I have found a page which does what I am looking for:
>
>http://jsfiddle.net/9Z363/93
>
>This seems a bit over complicated for doing such. There is surely something simpler.
>
>Basically:
>
>1. Left column is fixed
>2. Right column takes a much as possible
>3. Right column wraps as needed
>
>However, I would like the right column to always show a minimum of 260 pixels. So, when it cannot show 260 pixels, it will then wrap under the first column.