Some customers are afraid of buying online. Afraid that your company isn’t real. And a 3-year old copyright notice at the bottom of the page won’t raise their spirits. So do yourself a favor and keep it up to date. And while you’re at it, insert a time period like “Copyright (c) 2003-2008” to show how long you’re already in business.
If you’re lazy (just like me, I admit it), automate that with a tiny piece of PHP:
Copyright © 2003-<?php print date("Y")?>
To make sure you’re always “alive and kicking”… 😉