I sometimes get an "Expired link" error. Alright. But then I have to go back to the cached page I came from, klick at the top (or ctrl+f5) to get back to the start page. Not good. I'd suggest putting a link to / on error pages.
Though I would like to see this actually implemented you may have better luck in the official suggestions thread <a href="http://news.ycombinator.com/item?id=363" rel="nofollow">http://news.ycombinator.com/item?id=363</a>