Turn Error Pages Into Opportunity

Two great examples of turning an error page into opportunity come from Wikipedia.

The genius of the wiki, as described by Ward Cunningham, comes from what happens when a page is not found. Generally the web site will simply say not found. On a wiki, the site puts up a data entry form and offers the user, the one interested in the content, to create the content. A dead-end error becomes an open door instead.

If you do put up an error message, for example when wikipedia's server fails, the outage message is also a call for monetary donations.

"Sorry- we have a problem... The wikimedia.org servers are currently overloaded, or down. Hopefully this will be fixed soon; please check back in a few minutes, as the problem is most likely temporary.... Donations Due to the ever-increasing number of people visiting Wikipedia and its sister Wikimedia projects, we have a constant need to buy new hardware to keep the site running. If you'd like to help, please donate. "