Non onload blocking async JS
http://www.phpied.com/non-onload-blocking-async-js/
http://tokkonopapa.github.io/Non-Onload-Blocking-Async-Evolved/
http://www.phpied.com/non-onload-blocking-async-js/
http://tokkonopapa.github.io/Non-Onload-Blocking-Async-Evolved/