You had published and deployed your application to the web, and the default error page that ship with the template will give the following instruction. Which means the user will see the same page when an error occurred. Best practice is to change the instruction into something more instructive for the user.
Instead of just words, you could put an error icon followed by “An error occurred while processing your request, try again later. If error persist, contact the administrator.”
No need to mention to the user, how to enable the development mode and other instructions. These instructions made and shipped with the template. The developer as the user will see exactly this page in production. In development, the developer will get much details about the error.
