.htaccess style error pages
In the root of your website (/www) you can create a file named .htaccess with lines for each error code and what page they should go to.
ErrorDocument 403 /error.html
ErrorDocument 404 /notfound.php
In that example, attempts to load pages that are "forbidden" (usually by access control) will see error.html located in your /www folder. Also in that example, attempts to load pages that no longer exist will display the php file notfound.php also located in /www.
Here is a list of Error Codes that can appear:
||Internal Server Error|