I decided to re-design my 404 pages, and I thought the following points I learned so far are somethings one can consider in making a good 404 page. A customer hard earned might be gone if 404 pages don't provide 'come back' messages.
404 pages should:
similar to the rest of the pages excluding the header and menu destractions
be written in plain relevant language (should clearly mention it is an error page)
include links to the home page, sitemap
include search functions if available
email address or email this error reports (visitors might let you know how that happened)
include the proper status in the server header Add humour but don't get too smart about it:
A recent 404 page I came across (misses the point I guess)
"Despite searchers' best efforts, recent reports from the field indicate that 404 is still missing. " Way to do it ( .htaccess)
ErrorDocument 404 /errs/404_custom.html Related: cool URLs don't change [w3.org]
