Doh!

Rats. After all the tinkering with the stylesheets, I just realised that I left the site overnight with no default stylesheet. So if you'd viewed the site before; no problem, the relevant sheet would have been identified from the cookie set on your last visit, but if you hadn’t visited before, you would have got no stylesheet at all. So apologies to my many insomniac / overseas readers. (I’ve now set the new grey look as default).