Extension:DismissableSiteNotice

The DismissableSiteNotice extension allows users to close the sitenotice, using cookies. When you add a new sitenotice and want everyone to see it, change the number on the created page MediaWiki:Sitenotice id by one (e.g. if it would be 5, you'd replace the page with the number 6 and so on).

Installation
To install DismissableSiteNotice, download the latest snapshot and extract it to your extensions directory. Then, add the following line near the end of your LocalSettings.php: