Alert messages are produced using the custom Polymer element
rhodecode-toast which is passed a message and level.
There are four types of alert levels:
ex. updated settings, deletion of a repo/user
ex. a gist which was updated elsewhere during editing, disk out of space
ex. a form not submitted, repo creation failure
ex. notification of new messages, invitations to chat
Whether singular or multiple, alerts are grouped into a dismissable panel with a single "Close" button underneath.