Be aware that the CSS for these layouts is heavily commented. If you do most of your work in Design view, have a peek at the code to get tips on working with the CSS for the fixed layouts. You can remove these comments before you launch your site. To learn more about the techniques used in these CSS Layouts, read this article at Adobe's Developer Center - http://www.adobe.com/go/adc_css_layouts.
Because all the columns are floated, this layout uses a clear:both declaration in the footer rule. This clearing technique forces the .container to understand where the columns end in order to show any borders or background colors you place on the .container. If your design requires you to remove the footer from the .container, you'll need to use a different clearing method. The most reliable will be to add a <br class="clearfloat" /> or <div class="clearfloat"></div> after your final floated column (but before the .container closes). This will have the same clearing effect.