So now you have a page that matches your site, and has “404 Not Found” on it, however it’s still rather boring and doesn’t really give anything you can do. Maybe add a link to your homepage or a search box to help get your visitors on the right track.
I particularly like GitHub’s 404 page, as it has a neat animation that reacts to your mouse, a search box and some links to see the site’s status. Try to find some 404 pages you like, and take bits and pieces from each of them.
To help you along, here’s some more 404 pages I like:
Hopefully those examples gave you a bit of inspiration for your own 404 page.
Here’s what it comes down to: make sure you tell the user why they are seeing the page and what they can do to continue, and don’t bombard visitors with information or clutter.
Additional editing by Haden