Well, not exactly. The web page has code that says "go to this https adserver and get an ad and place it here". Diversion intercepts the adserver lookup and instead of responding with the real one, responds with the pixelserv address. The web page goes to the pixelserv address and pixelserv immediately responds with a single pixel. But the web page also says, in effect, check that the certificate of the adserver is "xxx", sees that pixelserv isn't that, and drops the pixelserv response and puts, usually, a broken link box instead of the invisible pixel. Diversion without pixelserv sends the adserver lookup to oblivion, the webpage times out and presents the broken link box instead of the ad. The difference is measurable: the NYT home page loads in a second or so for me with pixelserv, and 6 or 7 seconds without.