JSFiddle - React, Tailwind, and code Playground

HTML

<div>
 teting testin
</div>
<div class="overlay">
    <div class="progress">
       <img src="@Url.Content("~/content/images/loading.gif")" />Loading...
    </div>
</div>

CSS

.overlay
{
    position: fixed !important;
    position: absolute; /*ie6*/
    background-color: #000;
    filter: alpha(opacity=20);
    opacity: 0.2;
    -moz-opacity: 0.2;
    -khtml-opacity: 0.2;
    -webkit-opacity: 0.2;
    z-index: 10004;
    display: none;
    filter: progid:DXImageTransform.Microsoft.Alpha(opacity=20); /*ie6*/
}
.overlay .progress
{
    position: absolute;
    z-index: 10005;
    background: #fff;
    color: #000;
}

JavaScript

$('.overlay').css({ height: $(document).height(), width: $(document).width() }).show();

$(".progress").css({ top: $(window).height() / 2, left: $(window).width() / 2 });