I'm redesigning Tar Heel Reader in hopes of taking load off the server and making the site friendlier to tablets and phones. Over the last few weeks I did a mockup with jQuery Mobile that works well enough on mobile devices but it was just kludged into the current system and it didn't work at all on IE6. So, I've decided to back up and rethink things.
I began to think about instrumenting the site to collect some statistics when I looked at the php code for rendering book pages. Incredibly, I had already encoded the information I needed into image URLs! I have no recollection of doing it but years ago when I wrote the code I added the query parameter
To confirm this analysis I used Info Sniper to lookup a small sample of the IP addresses; they look like schools and homes, not bots. I also examined the user agents; again they looked reasonable for browsers includeing various versions of IE, Safari, and Firefox.