You will probably have noticed by now that hen you miss type a URL or go on a website that doesn't exist you usually get a 404 page or similar. Some website leave it as a boring default, but some get creative and change the style and text.
Although many of these don't have that much useful information they are well designed and some are down right funny.
If you click on the image you will get a full size version. In no particular order:
1) TV Links

A great website where you can get links to TV shows, this is a really good error message because it continues in the style of the website.
2) Google

A bit boring and not as interesting as some, but the cool retro look is great.
3) Orkut

4) Reddit

5) Torrentz

6) Apple

7) Blogger

8) Digg

9) eBay

10) Fark

The only reason this is here is because of the chipmunk thing. Very funny.