We’ve covered how to optimize your 404 Error page for search engine optimization (SEO) purposes in the past, making sure all of those dead links out there on the web don’t penalize your web site.
The implementation of a Site Map on 404 Error Pages is one way to do so.
Many websites suffer from error or badlinks from years of being linked to. Instead of receiving an error message, users are taken to an optimized navigational table of contents which can then lead to a conversion or sale. Plus, this helps to solidify sound search engine placement.
One hardcore example of 404 Error Page optimization is at Search Engine Watch. Their 404 page includes links to popular sections & archives, a link to their own search engine, site map links and of course, a link to their homepage.
As a matter of fact, the Search Engine Watch 404 Error page is so hardcore search friendly that it ranks #2 in Google right now in the results for “Search Engine News.”