Recently I designed a page and fought a bit with screen size issues… I ended up using a Javascript solution. The script detects the browser window's width, then displays a picture based on how much room is available. If your window size is greater than 800, you see a picture of a lady. If it's 800 or less, you see a very narrow picture of a guy. To test it, visit Kakoon.com , then resize your browser window and reload the page. I found the script for it at javascript.internet.com - one of my favorite reference sites.

Also during this project I wondered how many people were still using the smaller screen sizes, and I found my answer at - where else - the W3C web site. They have a great Web Browser Statistics and Trends page.