The Simplest Way to Load CSS Asynchronously | Filament Group, Inc.
Scott re-examines the browser support for loading everything-but-the-critical-CSS asynchronously and finds that it might now be as straightforward as this one declaration:
<link rel="stylesheet" href="/path/to/my.css" media="print" onload="this.media='all'">
I love the fact the Filament Group are actively looking at how deprecate their loadCSS polyfill—exactly the right attitude for polyfills in general.