JSFiddle - React, Tailwind, and code Playground

HTML

<div id="labelHolder">
    <label id="lblStatus">Please wait...</label>
</div>
<button id="btnClose" value="Close" onclick="window.close();"></button>

CSS

#labelHolder {
    text-align:center;
    vertical-align:middle;
}
#labelHolder #lblStatus {
    margin: auto;
    position: absolute;
    top: 50%;
    left: 0;
    bottom: 0;
    right: 0;
}
#btnClose {
    position:absolute;
    bottom:0;
    left:50%;
    margin-left:-40px;
    text-align:center;
    width:80px
}