Don't use URL parameters if you can avoid it

Parameters on URLs make them long and hard for anyone to read. And search engines can get confused by them, especially if the parameters are meant to hold customer information, and not indicate a separate Web page. Also, as I mentioned elsewhere, search engines don't always rank dynamic pages as high as static pages, and most dynamic pages use parameters on the URL to indicate the correct page. If you must use parameters, you might want to consider doing a URL rewrite to static URLs, at least for your most important pages.