JSFiddle - React, Tailwind, and code Playground

HTML

<div id="overlay" class="overlay">
     <img src="http://cd.centraldesktop.com/publicfiles/media/socialbridge/demo/images/loading.gif" alt="Loading" width="25%" style="margin-top:5%;" />
     <br />
     <h1>Loading...</h1>
</div>

CSS

.overlay {
    background:#666666;
    opacity:0.7;
    filter: alpha(opacity=70);
    position:fixed;
    width:100%;
    height:100%;
    text-align:center;
    top:0px;
    left:0px;
    z-index:1000;
}