JSFiddle - React, Tailwind, and code Playground

HTML

<div class="holder">     
      <div id="popup" class="popup">            
            <div class="content">
                        some lengthy text
                     </div>
</div></div>

CSS

.holder{        
    width:100%;
    display:block;
}
.popup{
    width:800px;
    border-radius: 7px;
    background:#6b6a63;
    margin:30px auto 0;
    padding:6px;
    position:absolute;
    left: 50%;
  top: 50%;
  margin-left: -400px;
    margin-top: -40px; /* This should be half of the total height of your div */
}

.content{
    background:#fff;
    padding: 28px 26px 33px 25px;
}