If your not already familiar with it, check out the ExtJS library for all the core files to this demonstration.
Ok, so traditional message boxes are....well they're functional. But with the net being driven towards aesthetically pleasing, web 2.0 standards, it's important to get the right look for your site!
Attached is JS code taken from the ExtJS site, and modified to automatically display the message box when the file is loaded. To stop this happening constantly, simply surround it by a <cfif>, like so:
<cfif structKeyExists(attributes,"updated")>
<script type="text/javascript" src="/ext-2.0/examples/message-box/updated.js"></script>
</cfif>
So when you relocate after an update, add ?updated=1 in the link and it will display a lovely message box :)
P.s. this was using Ext 2.0
Example here