Forum:Dismissible messages

Could someone please direct me to a page that tells me how to make a message, that will appear at the top of all pages on a wiki, and can be dismissed if the user wishes. Such as the one, currently telling users to change their bookmarks, on the Redwall wiki (w:c:redwall).

Thank you,

WHLfan (talk to me!) 01:31, 28 July 2008 (UTC)
 * Just change MediaWiki:Sitenotice to your desired message. Every time you change the message, though, you need to change MediaWiki:Sitenotice id to the next highest number.  There's also MediaWiki:Anonnotice for a message to anon users. swannie 02:01, 28 July 2008 (UTC)