Bob. July 13, 2003. A little snag.
I had rewritten the front page to generate its content dynamically, using PHP to pick up a fixed number of entries and shunt the rest onto an archive page. (See link at the bottom of the main page.) To do this, I used a particular PHP function that was only supported in PHP versions >=4.3.0. The host machine for our domain reported that it supported PHP 4.3.1, and when I tried it, it worked - all well and good.
Until 24 hours later, when it mysteriously stopped working, and the front page would only display a fatal PHP error. Imagine my surprise when I checked the server's PHP version again - as of today, it's 4.2.3. Apparently our hosting service has backed down their version of PHP to an earlier release - no explanation why, either.
In any case, PHP's online manual held the solution: a custom version of the filename matching function that I simply cut-and-pasted here. Ah, the joys of webmastering.