Error pages inform visitors about problems when they attempt to access your site. Each problem has its own status code (for example, 404) and error page.
To customize an error page, perform the following steps:

1 – Open cPanel (yourdomain/cpanel).
2 – Click on (Error Pages) from Advanced section.
3 – If this account manages more than one domain, select the domain for which you wish to edit an error page from the Managing: menu.
4 – Click the error status code for which you wish to edit its error page.
5 – Enter a message in the text box.
6 – Click Save.