For a website to appear slick it should load within 1 second on Wi-Fi and 2 and a half seconds on 3G.
Inlining to enhance performance:
inlining – serve up some CSS in the same file as the markup, which reduces the number of server requests for a page. When the browser encounters externally linked CSS it will effectively stop everything its doing, the request, download and parse the CSS. Then it will go back to rendering the page.
Develop code in silos, then optimise afterwards, hopefully tools can automate inlining as a production step.
A Book Apart 13 “Responsible Responsive Design” – Scott Jehl
HTTP/2 vs HTTP/1.1