The Big Red Fez."
If you have a search box on your website, Godin tells us, and a visitor uses it and there isn't a single thing on your site that matches their search criteria, don't serve them a message that says "we don't have what you're looking for".
Instead, show them a list of the five most popular things on your site that people search for. Coax them to re-enter the search criteria with different wording. Offer them a discount coupon for your most popular item.
You have a potential buyer on your site. Sell them your software!