With Google and their apps like Search, Docs or GMail only a very small time is actually spent in the initial page load, writes Andreas Grabner in a recent blog post. Of course, much time is spent in JavaScript, XHR Calls and DOM Manipulations triggered by user actions. Grabner writes:

It is very important to speed up Page Load Time – don’t get me wrong. It is the initial perceived performance by a user who interacts with your site. But it is not all we need to focus on. Most of the time in modern web applications is spent in JavaScript, DOM Manipulations, XHR Calls and Rendering that happen after the initial page load. Automatic verification against Best Practices won’t work here anymore because we have to analyze individual user actions that do totally different things. The way this will work is to analyze the individual user actions, track performance metrics and automate regression detection based on these measured values.