Login to cPanel.
Locate Advanced tab and click Error Pages.
Select Domain to Manage Error Pages. There will be a dropdown box where you can select what page you want to add an Error Page.
Edit Error pages. There will be 2 tabs, Edit Common Error Codes and Show All HTTP Error Status Codes.
Select an option from those 2 tabs, and click the selected error page to edit.
You can edit the error pages for the selected domain. After you edit, click Save.
