Hi,
The Scrolling Gallery uses Abode Flash Player. If a system doesn't already have Flash Player installed, it will get that message as a prompt to install the software.
If you are seeing the message, it must be from a system without the player. You can install Flash Player here.
http://get.adobe.com/flashplayer/
I looked at the page, and the Scrolling Gallery is OK (no problems).
Danno