ErrorDocument 400 /errors/400.html ErrorDocument 401 /errors/401.html ErrorDocument 403 /errors/403.html ErrorDocument 404 /errors/404.html ErrorDocument 500 /errors/500.html
This tells the server that each of these errors pages are in the /errors/ folder and the exact file that needs to be seen when somebody encounters that error.
Each line represents one error. For example, this
ErrorDocument 404 /errors/404.html
is the line for a 404 error, or the message you get when a page can not be found. You can change the path of the file you want the user to go to when they run into the error as well. Just change the “/errors/” to another path like “/static_pages/404.html”.
If you need to get more information on customizing your 404 error page, please check out this thread from the cPanel forms.