The future of loading CSS - →

The plan is for each <link rel='stylesheet'> to block rendering of subsequent content while the stylesheet loads, but allow the rendering of content before it. The stylesheets load in parallel, but they apply in series. This makes <link rel='stylesheet'> behave similar to <script src='…'></script>.

Almost four years ago, Jake Archibald described how we could get progressive loading of CSS files by placing the references inside the <body> element.