Well spotted, Jez! You're right, I broke it. Now I feel silly -- I didn't even realize! I'll attempt to put it back this evening. Apologies to all affected.
The explanation is that the person who made the style that we use on here released an updated version, so I updated this site's version, checked to make sure that nothing was seriously affected (and fixed things that I had noticed), then moved on. You may also notice that the navbar has disappeared, and now there's just the top one which is done by images. How do you get to the Arcade and Chat you may ask? No worries -- I've put them into the Quick Links pulldown box so we don't have to worry about extra links anymore.
Still, apologies about the mood hack. As I said I will put it back this evening.