Perhaps you’ll have seen this already but we thought it worth sharing.
http://www.thefirstwebsitewithnohome.com
It reminded us of an idea we had for sponsoring error 404 pages. For when people have lost their way, or the webpage they’re looking for has gone missing – this could be a nice adspace opportunity for a charity for Missing Persons. Maybe bridge the gap between a trivial loss (a web page) and a more poignant one (a loved one) – by bringing up all the faces of the world’s missing persons round the world, followed by a call for donations.
Or, you could do something much more light-hearted and make an ad for TFL’s Lost Property.
By the way, I have no idea why the spacing has gone awry on this post. Hope it’s just about readable.