The DOM and all additional resources don’t need to be parsed, the client can already begin the download of the
screen.cssresource, without “wasting time” processing the DOM and all external resources, only to make a new request to the server to begin fetching them.
When you add this all up for all resources on a page, this can easily save 100-200ms of the total page load/paint of a website. Those are numbers that should really have you consider implementing HTTP/2.
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