Add a Message of the Day extension for Review Board 2.0+.
This extension allows an administrator to display a message to all

visitors to that Review Board server. This can be used to announce

incoming downtime, or a recent upgrade. It can also contain links and

other HTML formatting.
Users can dismiss the message, and it won't show up again for that

particular browser, unless cookies are cleared, or a new message is

posted.

Tested a variety of messages on Chrome and Firefox.


Tested dismissing and making sure it stayed dismissed, even on cached pages.