"System Message" page (when submitting donations, membership requests in quick succession - not deep-linkable).

Current status "There should be a headline. Those rather short messages might be missed." (@kai.nissen)

The headline should be "Fehler" (as used in the current skin as well). The message is passed to the template as a twig variable (message). Please refer to any static content page (e. g. Imprint) for styling.