I’ve resolved the very significant problem that was preventing people from reading post pages or leaving comments. (Thank you to Gábor Bernáth, who provided some third-party TCP captures.)

I’m not quite sure what this has cost me in terms of regular readership. (I know there weren’t many of you to begin with.) But I’m hoping this is the last time it’ll happen. Read on if you care about the details.

It turns out that Apache’s mod_disk_cache was causing the problem. It took me a while to solve, though, because the issue was difficult to reproduce. Internet Explorer wouldn’t stop sending If-Modified-Since headers, which raised problems. Firefox, on the other hand, would only show the problem once, and then start working normally. A few days ago I did try turning off Apache caching, but I had no idea whether it solved the problem, or whether the problem was just intermittent.

And none of this would have been easy to solve on Windows. Using an Ubuntu machine, it was so simple. Wireshark captured the TCP packets and netcat helped me try different header combinations until I could reliably reproduce the problem. With a repeatable test, I just tweaked Apache until the problem stopped.