A 404 error page is a page your visitor encounters when there is a page or a blog post missing on your website. In the course of many months and many years when you are constantly adding new web pages and modifying or removing redundant pages there comes a time when the search engines and other websites still point to links on your website that are actually not there. In the case of a missing 404 error page either the browser shows the default “page not found” error, or some web servers redirect the visitors to the home page.
Both these settings have negative sides but when the user’s browser shows its own page not found error he or she might think that there is some problem with the entire website, or worse, the website has ceased to function. 99% of your visitors are not going to take trouble and try your home page URL; they will simply leave. The same will happen with search engine crawlers. If they don’t see the page they are trying to crawl, they may think there is a problem with the website and consequently the search engines may downgrade your rankings.
If your visitors are quietly redirected to your home page whenever they visit a missing link they may think you have created doorway pages. The search engines may feel the same thing, and again, may downgrade your rankings.
The best thing to do is create an effective 404 error page. 404 is an error number the servers generate when they cannot locate the page you are trying to visit. By creating a 404 error page you tell your server what page to visit in case the visitor ends up on a non-existing page.
An effective 404 page not found error page tells your visitor what has happened and suggests other steps, for instance, visiting related links, or presenting a sitemap. This blog post explains how to show a custom 404 page not found page on your website.
And this blog post showcases some interesting and amusing 404 error pages.