When your app is crashed, out of resources, or misbehaving in some other way, Heroku serves an error page, which can be customized for each application.| devcenter.heroku.com
Heroku’s maintenance mode feature serves a static page to all visitors, allowing developers to perform maintenance tasks that require the absence of incoming traffic.| devcenter.heroku.com
This article describes the restart behavior of Heroku [dynos](dynos) and how to restart them.| devcenter.heroku.com