Short and sweet, I don't suppose you'll need more detail than this:
We host our website on an in-house webserver.
A catastrophe has and will happen again where communication from the web into/out of our building ceases.
When this happens, we'd like our users to at least see some kind of "down for maintenance" or other message (twitter's Fail Whale?) when trying to access our site, rather than the current "server not found" type messages that they currently get. (A static server, temporary redirects for all requests).
[Being able to fail-over to a fully functional website would be awesome, but is not required, and probably not an option].
Obviously there has to be some kind of off-site failover that could take over when our local servers are down.
How is such a solution implemented? Other suggestions?
EDIT: If I'm not using (or leaving out) some correct terminology for this, let me know!