HOWTO: Foreground images that scale with the layout
From the blog:
Simple CSS techniques can make the content images inside your liquid or elastic pages scale with the layout.
This tutorial is slightly adapted from Chapter 9 of my book, Flexible Web Design: Creating Liquid and Elastic Layouts with CSS. You can download most of Chapter 9 for free as a PDF at the Flexible Web Design companion site, as well as download the HTML, CSS and image files that go along with this tutorial.
Since the area available for an image to display within a flexible layout changes on the fly, your images may need to as well. While fixed-width images can work within flexible layouts—as long as they’re not too large, or you have matching minimum widths in place—there are lots of ways you can dynamically change the screen area that an image takes up.
One way to dynamically alter the footprint of an image is to make it literally scale, based on either the text size or the changing dimensions of its parent element. Both are elegant effects that are deceptively simple to create.