CSS выравнивает предметы вертикальный центр
.parent {
display: flex;
justify-content: center;
align-items: center;
}
Gleaming Grivet
.parent {
display: flex;
justify-content: center;
align-items: center;
}<style>
body { background: white }
section {
background: black;
color: white;
border-radius: 1em;
padding: 1em;
position: absolute;
top: 50%;
left: 50%;
margin-right: -50%;
transform: translate(-50%, -50%)
}
</style>
<section>
<h1>Nicely centered</h1>
<p>This text block is vertically centered.
<p>Horizontally, too, if the window is wide enough.
</section>