What exactly is being said on slide #45? Initially I thought it said that perceived rendering time is less when as much content is presented prior to the javascript executing (which is my experience, anyway). But does it then say that this was not the case with IE?
That slide is a bit confusing. At first it seems to be condoning the use of CSS background images to give the perception of faster loading, but then he says that it was bad for IE ... which effectively is saying you shouldn't do it. That slide is useful because it should instantly discourage anyone looking to implement a technique like that.