Creating customized error messages
There is nothing more frustrating then getting to a page which no longer exists and getting the dreadful plain looking 404 error page with no explanation of what just happened. These pages can be made much more informative with simple HTML. If you take a look at the following links to pages that are broken you will notice that we’ve made them a bit friendlier:
The folks at the BBC display the 404 error message, but at least they have added some additional information giving you options as what to do next which is not the case over at crap.com.
Of course you can also use humour to display your error messages. Kate discovered this great message when she broke her Twitter.

I think that your website users would appreciate your effort.