UNIX Error Pages
.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.
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.