I found a nice slideshow by Google’s Ilya Grigorik a few weeks ago, taking an overview of the essential issues in optimizing initial web page render time.

The talk was mobile-oriented, but many of the same concerns apply to desktop sites. You can find the slides on Ilya Grigorik’s blog

Some key points:

• 4G is not a ‘magic bullet’ for mobile performance problems. Our customers are going to be stuck with 3G for quite some time, and TCP-slow-start imposes harsh bottlenecks.
• Waking up the radio on mobile devices is slow. Radio is typically turned off after idling for 100ms; subsequent requests suffer a significant warm-up penalty, even on 3G (where it can be up to 2.5 seconds)
• Rendering is blocked as the browser constructs the DOM and CSSOM. Inlining ATF (above-the-fold) styles and bootstrapping further styles asynchronously may be a useful strategy
• Inlining styles for above-the-fold content might be a wise strategy