The Summer mood seems to be settling in at last, with today being a rather quiet and uneventful Monday (crammed with calls, meetings and informal status updates, but without the usual GTD stress).
Not much in the news either (yet, have barely glanced at them). Got mildly Scobledotted (barely a tickle, actually, but it prompted me to make the time limit on site comments more obvious to visitors), and (via the spool) saw that Andrew found the answer.
His piece is a must-read on the wild and wooly uses of HTTP headers around the net, and it ends with him finding the remnant of my extensive HTTP and RSS caching optimizations around If-Modified-Since and other dances with proxies.
Since I spend quite some time looking at how phone vendors and WAP gateways mangle the HTTP protocol I rather like using HTTP headers for debugging (X-Debug being the obvious choice), since they can often provide some interesting hints as to what actually gets through.
A couple of months back, for instance, Andrew would also have gotten a X-Random-Hash and an X-Optimize-This on most pages...