I've filed a request with my service provider to update the server to a new version of the HTTP server and OS. The site will be offline for up to a few hours (barring anything catastrophic).
As Sam (the man) Jackson says in such circumstances, "Hold on to your butts!"
Update: 4:47PM PDT
The site is up but has moved to a new IP address. It may take several hours for DNS caches across the 'net to resolve to the new address. In the mean time you can access the site via:
Update: 5:28PM PDT
At least for me, http://travellermap.com is resolving. It may take several more hours for that address to resume working for you, so use the temporary URL above if necessary.