Firefox and Opera are the only browsers capable of loading scripts in parallel while preserving execution order. In all other browsers, scripts must be loaded sequentially.
//只有Firefox和opera支持并行加载脚本，并保持执行顺序。其他游览器必须按顺序进行加载。
All browsers respect css specificity based on the order of the link elements in the DOM, regardless of the order in which the stylesheets are actually downloaded.
//所有游览器根据link在样式表的顺序进行渲染，而非根据最终下载时间。