These numbered error codes are how the Web server tells the user about a status or error encountered. There are many different error codes that a server can deliver, but these are a few of the more common codes.
401 – Unauthorized Access to the URL resource requires user authentication which 1) has not yet been provided or 2) which has been provided but failed authorization tests. This is commonly known as "HTTP Basic Authentication". Unless you have a good reason to do so, it is not recommended to redirect a 401 error.
403 – Forbidden The request was a legal request, but the server is refusing to respond to it. Unlike a 401 Unauthorized response, authenticating will make no difference. This is usually due to a scripting or permission(s) issue.
404 – Not Found This response code indicates that the client was able to communicate with the server but either the server could not find what was requested, or it was configured not to fulfill the request and not to reveal the reason. Error 404 should not be confused with "server not found" or similar errors, in which a connection to the destination server cannot be made at all.
500 – Internal Server Error Your Web server encountered an unexpected condition that prevented it from fulfilling the request by the client (e.g. your Web browser) for access to the requested URL. This is a 'catch-all' error generated by your Web server. Basically something has gone wrong, but the server can not be more specific about the error condition in its response to the client.
What are custom Error Code pages?
Instead of seeing the default error message, you can create your own error pages by adding special command lines to a .htaccess (pronounced dot h t access) file. This file typically lives in the /public_html/ directory in your account. Or if you have add-on domains, it lives in /public_html/{add-on domain}/. You may already have one in there. If that is the case, then you can just add these lines to it. Otherwise, you can just create a new, empty, .htaccess file to add these lines to it.
The format for an ErrorDocument statement in a .htaccess file follows:
ErrorDocument CODE URL
The CODE refers to the error code you wish to redirect (403, 404, 500, etc) and URL refers to the location of the file you would like displayed. The URL can either be a URL-Path (e.g. /errors/404.html) or a full URL (e.g. http://www.example.com/404.html). For an addon domain or subdomain the error page path must be a full URL.
Examples
If you have created a 404.shtml and uploaded it to the root directory of your domain example.com, page your .htaccess file would have a line like this:
A .htaccess file controls the directory in which it sits, and all subdirectories. However, by placing additional .htaccess files in the subdirectories, other .htaccess files can be overruled.
