There are a number of default pages that you should skin to match your site; otherwise, they will be Symfony branded. These include the error 404 page, the error 500 page, and the maintenance and security pages.
Apart from the error 500 page and the unavailable page, the rest are all located in Symfony's default module. Therefore, to change these pages, we can follow one of these two options:
In your Symfony installation, there is a default module. For example, the default module on my installation is located in the
/usr/share/php/data/symfony/modules/default
directory. If you copy this entire folder into your frontend and backend application folders, it will override Symfony's module in the installation. This default module contains all of the default actions and templates for the error 404, login, secure, unavailable, and disabled pages.You can amend the application's settings to reflect your specific locations located in the
apps/app_name/config/settings.yml...