Right up-top there in the usability stakes is the fact that you should always give your visitors what they want. That’s tough, especially when the page they end up with is “Error 404”. I’m not going to go off on a rant about what you can do, but what I do is thanks to a few neat Wordpress Plugins.Basically, the 404’s you’ll see on Psyked contain a few elements - A search box, related links, top categories and top posts.
Search box, that’s easy, it’s inbuilt into most themes. Top categories and posts are thanks to the plugins "Most popular categories by posts"and “WP-PostViews”. Related links is an impressive plugin, “Related Posts” - there’s a version specifically for 404 pages.
Have a look at the result…