Custom Error Messages Tutorial Author - Man1c M0g (http://forums.biorust.com/member.php?s=&action=getinfo&userid=1)

It is a fact of life that if you run a busy regularly-updated website you'll also move your files about quite often. Whilst this may not pose a problem for you initially, search engines take a while to process dead links, and during this time you may be losing visitors who go to your old pages and get the standard 'page not found' error. You can prevent this by customizing your error pages, sending your visitors instead to a nice formatted webpage that politely tells them to keep on looking using your new navigation structure.   There are two ways to do this...

Apache Configuration
If you are lucky enough to have a decent web hosting service that gives you access to Apache's httpd.conf file, you can set up custom error messages in a matter of moments.  Just open up the file in your favourite text editor, search for ErrorDocument 404, uncomment out the line, and add the URL to the file on your website containing the error message.   You should end up with a line looking something like this:

ErrorDocument 404 http://www.yourdomain.com/404error.htm

Now save your changes, upload the amended file, and restart Apache.  If all goes well, you'll now be redirected to your error page if you enter in an incorrect URL on your server.    If you have IIS or any other webserver, access your documentation for details on how you do this for your service.

.htaccess Configuration
Even if you don't have direct access to the Apache configuration files, all is not lost. A virtually identical effect can be achieved using local .htaccess files.   Just use your favourite text editor to create a file called .htaccess (if you use notepad, beware it doesn't add a .txt extension onto the end) that contains the following code:

ErrorDocument 404 http://www.yourdomain.com/404error.htm

Notice anything familiar? :)  Now upload the file to the main directory of your website, or the specific subdirectory you want to protect.  Remember that the settings in this file will affect any directory you put it into and all subdirectories branching off from it, but not any parent directories.  Also make sure you upload this file in ASCII and not binary, and CHMOD it to 644 or you'll run into problems. If you don't know how to CHMOD, just download a decent FTP program like CuteFTP, right click on the file, and select 'change file attributes' or somesuch - that does the same (essentially it just allows the file to be readable by the server but not by any joe public with a browser).   And that it!  No reset is needed, so you should be able to see your changes immediately.

Other Configurable Errors
Although 404 (page not found) errors are by far the most common ones you will see on the internet, there are quite a few others that can be handled using exactly the same methods detailed above. Just in case you ever wanted to know, they are...