Years ago, when using CSS for layout was still rather new, one of the common arguments for using CSS instead of tables for layout was that it enables you to change the layout order without editing your markup.
A typical example is a page with a vertical sub-navigation to the left, a centered content area, and a sidebar to the right. If you use tables for layout you will need to change the HTML to move the columns around, say if you wanted the navigation on the right and the sidebar on the left. With CSS you can change the visual order of the columns without touching the HTML.
But, there is a but.
Posted in Accessibility, CSS.