How to speed up website or how to load css and javascript files async

To load css and js asynchronously

For stylesheets

Use this way
@import url('css/jquery.material.form.css');
instead of
<link rel="stylesheet" href="css/jquery.material.form.css" />

add defer attribute to load java script files async
as shown below
<script type="text/javascript" src="js/jquery-2.0.3.min.js" defer="defer"></script>