Error 404: Page Not Found. Just kidding.
Notfound.org
Notfound.org is a way for webmasters to make better use of their 404 error pages. Instead of displaying a standard message, the Notfound project wants you to install their program so a missing child's picture and details are automatically shown.
Currently, over 2000 websites have signed up.
bluedaniel.com
A beautifully designed 404 page, bluedaniel.com gives its users an animated page of a train leaving track 404. Complete with sound and impressive graphics, this example shows what designers can do when they put their minds to it.
Zug.com
Zug.com has attempted to inject some humor into the annoying process of encountering a 404 by reminding their users just how many things go missing or AWOL in their daily lives; whether it be the sock that went into the washing machine and never came out, or the ever-elusive pen.
Kevin Michael Smith
Photographer Kevin Michael Smith gives his users a a 404 page that more closely resembles a frequently asked questions board, offering tips and advice on how next to proceed through a rather cool flow chart — as well as offering users the chance to head back and read a few of his articles.
DDZ.net
A fun take on the traditional 404 page, DDZ — otherwise known as gaming network Death DealerZ — have constructed an error page complete with as many street examples of "404" signs as possible.
Bringing religion into the equation?
Perhaps there is a divine reason you cannot find that particular page.
Overlawyered.com
Overlawyered.com, a blog that documents the state of contemporary policy and legal issues, uses its 404 page to touch upon an issue so often found across the net: copyright infringement that requires content to be removed and taken down.
Mspaintadventures
Found on Tumblr, this odd 404 page for mspaintadventures.com is certainly one of the most entertaining of the bunch. The 404 page hosts an animated cartoon complete with voice-overs and an amusing advertisement for the group's cartoons and merchandise.
scythe.com
Found on the appropriately named scythe.com, the webmaster lets you know that yes, it is all a conspiracy, people are out to get you, and the grim reaper will soon be paying a visit.
JibJab.com
Ecard website JibJab has attempted to use their 404 page as a way to reflect the humorous nature of their website, but frankly, it could be described as more creepy and less funny.
The blue screen of death
There's certainly no reason why a 404 page has to be boring, so why not give your users a heart-stopping moment if they happen to be fans of Microsoft's Windows operating system?
huwshimi.com
The guys at Huwshimi and Friends have their own well-illustrated, eye-catching design -- that of a ninja stealing the page you're after.