Apache allows you to customize the server at the directory level, using .htaccess files. This tutorial explains how to use them to serve custom 404 error (page not found), and other common error pages, to your users.
Server response codes
A server reponse code is a three digit number sent by a server to a user in response to a request for a web page or document. They tell the user whether the request can be completed, or if the server needs more information, or if the server cannot complete the request. Usually, these codes are sent ‘silently’ – so you never see them, as a user – however, there are some common ones that you may wish to set up error pages for, and they are listed below. Most people will only ever need to set up error pages for server codes 400, 401, 403, 404 and 500, and you would be wise to always have an error document for 404 errors at the very least.
It is also relatively important to ensure that any error page is over 512 bytes in size. Internet Explorer 5, when sent an error page of less than 512 bytes, will display its own default error document instead of your one. Feel free to use padding if this is an issue – personally, I’m not going to increase the size of a page because Internet Explorer 5 doesn’t behave well.
In order to set up an error page for any other error codes, you simply add more lines to your .htaccess file. If you wanted to have error pages for the above five errors, your .htaccess file might look something like this:
ErrorDocument 400 /400.html
ErrorDocument 401 /401.html
ErrorDocument 403 /403.html
ErrorDocument 404 /404.html
ErrorDocument 500 /500.html (more…)