JSFiddle - React, Tailwind, and code Playground

HTML

<div class="absoluteCenter">
     Content of DIV<br><br><br><br><br>Adds scrollbar when window is resized.
    </div>

CSS

.absoluteCenter {
     /* Must manually set width/height */
     width:200px;
     height:150px;
    outline:1px solid orange;

     /* The magic centering code */
     margin:auto;
     position:absolute;
     top:0;bottom:0; /* Aligns Vertically - Remove for Horizontal Only */
     left:0;right:0; /* Aligns Horizontally - Remove for Vertical Only  */

     /* Prevent div from overflowing main window */
     max-width:100%;
     max-height:100%;
     overflow:auto;
    }
    
    /* IE 7 and Below */
    :first-child+html .absoluteCenter,
    * html .absoluteCenter {
     /* Place code here to override all above values, and add IE friendly centering */
    }