StackOverflow has 503'd a lot recently. Time to get a better server? What is the cause of this error? It happens anywhere on the site, seemingly randomly.
The site was intentionally taken offline. A short message, the logo, and a graphic has been the standard offline message, but I suspect that in the switch to HAproxy they didn't account for what the site would look like to viewers when offline:
HAProxy doesn't like the app_offline file.
We do have to take the sites down periodically to apply critical Windows updates, and that applies to the database server (all sites down) as well.
'tis working now. The team warned about changing DNS - perhaps related to that? Or a new release of the software. Or just random stuff...