AskApache Google 404 is a WordPress plugin that uses some ajax code and a few tricks to display a very helpful and SEO Error Page. The default displays Google Search Results for images, news, blogs, videos, web, custom search engine, and your own site. It also searches for part of the requested filename that was not found, but it attaches your domain to the search for SEO and greater results.

Plugin Page

AskApache Google 494, Plugin, WordPress Plugin, 404