JSFiddle - React, Tailwind, and code Playground

HTML

<div class="block">
    <div class="centered">
        <h1>Some text</h1>
        <p>But he stole up to us again, and suddenly clapping his hand on my shoulder, said&mdash;"Did ye see anything looking like men going towards that ship a while ago?"</p>
    </div>
</div>

CSS

.block {
    text-align: center;
    background: #c0c0c0;
    border: #a0a0a0 solid 1px;
    position: fixed;
    top: 0;
    bottom: 0;
    right: 0;
    left: 0;
    font-size: 0; /*added*/
}
.block:before {
    content: "";
    height: 100%;
    display: inline-block;
    vertical-align: middle;
}
.centered {
    display: inline-block;
    vertical-align: middle;
    max-width: 500px; /*changed*/
    padding: 10px 15px;
    border: #a0a0a0 solid 1px;
    box-sizing: border-box;
    background: #f5f5f5;
    font-size: 16px; /*added*/
}