I believe he was looking pretty closely at the entire DOM rather than specifically innerHTML but I didn't really dig down on that. As for the browser mods, he

I believe he was looking pretty closely at the entire DOM rather than specifically innerHTML but I didn't really dig down on that. As for the browser mods, he controlled to look at the difference holding browser version/OS steady, so the changes would be consistent inside the browser,version,os pairing. It was a rather scientific approach imo.