As it turns out, I was a little premature in proclaiming XHTML compliance. I had used Dave Raggett's way-cool Tidy utility to clean up my code. I figured that was all I needed to do. Wrong. Tidy is utility, not a miracle worker.

Fortunately, the W3C has a spiffy markup validation service that can check HTML and XML files to see whether they're valid, comply with their stated standards, and so forth. It's free. It tells you, line by line, exactly what is wrong with your page. Once I got over my dismay, I set about fixing my pages. Now I'm proud to say that the home page, archive page, and haiku pages are valid XHTML 1.0 Transitional. Even the style sheet is certified kosher, thanks to a separate CSS validator.