In order to change the default Apache success page (the page that you see when you just type in the hostname for example) you will need to modify the /usr/local/apache/htdocs/index.html file. This is not documented anywhere on cpanel docs or forums (not that I could find).
To affect this change, you will need to login into your server via ssh then change directory to /usr/local/apache/htdocs
And then edit the file index.html
At this point you can edit the page to say whatever you eould like and even place a redirect there to push the user to whatever page you would like.
If you list the content of /usr/local/apache/htdocs you will see that you can also modify the content of other error pages that cpanel’s apache outputs.