Extension:PopupAlerts

The PopupAlerts extension allows to add popup alerts to wiki pages with an optionally specified expiration date so it can be controlled when (and if) users will see the popup again. It also has an integrated checksum-based invalidation mechanism to detect popup content change and hence reset the “already-seen” markers.

Usage
popup will be seen once in 100 years

popup will be seen once in one hour (3600 seconds)

Note: If you have many popups added to the page, only the first one will be taken into account. This limitation was added intentionally to prevent wiki pages from being spammed with popups.