from http://www.aaronpeters.nl/blog/why-loading-third-party-scripts-async-is-not-good-enough

delay-social-load.html

<script>
(function(w, d, s) {
  function go(){
    var js, fjs = d.getElementsByTagName(s)[0], load = function(url, id) {
      if (d.getElementById(id)) {return;}
	  js = d.createElement(s); js.src = url; js.id = id;
	  fjs.parentNode.insertBefore(js, fjs);
	};
    load('//connect.facebook.net/en_US/all.js#appId=changetoappid&xfbml=1', 'fbjssdk');
    load('//platform.twitter.com/widgets.js', 'tweetjs');
  }
  if (w.addEventListener) { w.addEventListener("load", go, false); }
  else if (w.attachEvent) { w.attachEvent("onload",go); }
}(window, document, 'script'));
</script>