Earlier this month we covered Google's revamp of their pagespeed insights tool, where they greatly improve the usability and details within the tool itself.
In short, Google wants your mobile pages to render really fast - not like the common page that takes 7 seconds to load but more like them rendering in a sub-second. Google is giving you advice on how to achieve that and then providing benchmarking testing tools to help you get there.
Google does clarify that the content above the fold is the main thing that should render immediately. And there are techniques to load such content first. The other best practices include:
- Server must render the response (< 200 ms)
- Number of redirects should be minimized
- Number of roundtrips to first render should be minimized
- Reserve time for browser layout and rendering (200 ms)
Pierre Far, from Google adds a lot more detail in human english on his Google+ page:
Finally, there is an important point here: The total loading time can still be more than one second (some pages simply need that), but because we've engaged the user very quickly, the perception the user gets is that the page is fast. To put it as +Steve Souders did earlier this year, we're not just webmasters, we're also "perception brokers":
Forum discussion at Google+.