are booked via mobile, and more than 50 percent of traffic arrives on Expedia Group sites via mobile. https://skift.com/2019/02/15/expedia-winning-at-mobile-in-southeast-asia-new-study/
factor in page abandonment and loyalty; 53% of users report that they abandon sites that take more than three seconds to load. - Slower sites are deemed lower in search engine ranking. Since 2018, Google has implemented site speed as a ranking signal in its mobile searches https://developer.akamai.com/blog/2016/09/14/mobile-load-time-user-abandonment https://searchengineland.com/google-speed-update-page-speed-will-become-ranking-factor-mobile-search-289904
CSS is render-blocking. • Make CSS as lean as possible on the first page load, in-line it. (This is why people put CSS in the head tag). • Usse media types and media queries to mark CSS as non-render-blocking.
the construction of the DOM. • Downloading, executing CSS, constructing the CSSOM blocks executing JS. • JS can make changes on both the DOM and the CSSOM.
resources by using: defer, async, code splitting, etc. • Minimize the number of bytes: minification, caching, etc. • If they must be downloaded, download them ASAP, or inline them. Every second counts!
setTimeout for delayed work. • Avoid long running tasks, it may eat up the next frame's budget. • Offload long running tasks to Web workers if possible, but there are catches.