tedster - 3:01 am on Apr 16, 2009 (gmt 0)

If it's a browser 301 for the customer's convenience

Or you could just serve the browser a true 404 http header with a custom page to help the use navigate the site. I have served the browser a carbon-copy of the home page on some sites, but as a different url. That's probably a better bet than playing with user-agent delivery whcih might be interpereted as deceptive cloaking in some situations.