After setting up the error pages in cpanel, you may need to adjust your browser settings to see this pages.

If you are using Internet Explorer:

Click Tools &gt; Internet Options &gt; Advanced and uncheck 'Show friendly HTTP errors'.

If you are using a different browser, check the settings and look for something that relates to errors.

Note: Custom error pages do not show up on temporary access url's (url's IP address, server name etc.) for your account.