We've all see it. It's the jolting error page you get when the page you requested from a server does not exist.

We regularly advise clients that 404 Not Found pages should be helpful and designed. Users may come across them if they have a typo in the URL, follow a link from an email that sometimes breaks URL's or if a search engine is pointing to a page that has been moved or deleted.

Some best practices around create a more user-friendly 404 Not Found page would be:

• Brand it. Make it like it looks like all your other pages. Include the site banner, and global navigation. Make it look part of your site - nothing is more disorienting to the user than losing the graphic consistency that identifies a site.
• Don't call it 404 Not Found. What does that mean to a regular user anyway? Tell them the truth in pain language, and be polite.
• Provide some useful links. When you lose your way you want to find some signs that will point you in the right direction.

Even with well-known site, some do it better than others.

Good examples:

• Apple - They provide useful links, but also use it as ad space. May as well, since you are on the site anyway.
• Microsoft - They provide a site map
• Jakob Nielsen's Useit.com - He still calls it "404 error message". Tsk tsk tsk.
• kottke.org - Jason Kottke provide an amusing intro, a search box and some useful links. Perfect 10.

Bad examples:

• Amazon.com
• Google
• University of Maryland

Some have even turned these pages into an art. Here's my personal favorite.

I have be admit with some embarrassment that our own 404 Not Found page does not follow our advise. Time to practice what we preach - I promise we will have a new, more useful 404 Not Found page within the next few weeks.

Update 11/08/2006
I just discovered John Maeda's post on this topic on his SIMPLICITY blog from 9/16. Nice comparison of Coke vs. Pepsi's error pages.