Unfortunately, it was out of our control - our hosting company were simply not serving the pages correctly. I am going to hound and pester them until I get an adequate response, so that I can give you all some assurance that it won't happen again. Watch this space.
MATT'S UPDATE: Surprise surprise, they have emailed me back saying it was my fault. I know it was not my fault - between the time the site went down and the time it was back up, I did nothing.
MATT'S UPDATE II: Okay, the next day they admitted it was their fault, and they don't yet have a resolution yet. So, there's not much I can do at the moment, except apologise in advance if the games stop working suddenly.