WordPress has a very nice Customizable Permalink Structure. Unfortunately with the new rewrite rules (using path info) all 404’s no longer get sent to the system logger.
That, my friend, is why you need the lovely Log 404 Plugin. Guess what? It sends all 404 requests to PHP’s system logger, so you’ll never miss a 404 again. And, it’s compatible with WordPress 1.5 and 2.0!