I've seen this idea before - i think there was a plugin for Firefox that you could use on an entire page - but this is a really, really classy implementation of way to inspect a particular element in a webpage.
So I'd read Darkness at Noon for high school but I don't think I realized it was fictional and not a memoir. I'm reading The Sleepwalkers right now, and I was wondering what the internet had to say about it/him. Turns out Koestler was sort of a weirdo.