A very cool and new (at least to me) concept: CSS media queries. This will allow us to set CSS for specific screen sizes: from the 480px wide handheld devices to the 1920px wide monitors.
Please note that this is different than the liquid/flexible layouts usually based on percentages. CSS media queries allows you to control layouts for specific screen resolutions.
Check out their example and resize your browser from really wide to really narrow to see the layout switch. Just don’t use a browser that starts with “IE”.