[Mediawiki-l] How to create a message on every Wiki page/article?

[Matt England]

How can I, as a MediaWiki admin, create a message on every Wiki page/article?

(In my current case, I'm running MediaWiki on a server/domain that will 
change in the upcoming weeks, and I want to put a msg at the top of every 
page that reads something like "Please note:  xxxx.com is a temporary 
location.")

The only thing I figured out was:  {{global_header}}

...but this requires that every author inserts the above text into every page.

Do any automatic facilities exist?  I've been hunting around the Template 
help stuff, but haven't yet found anything.

Thanks for any help,
-Matt