Here's a method using display:flex
:
.container {_x000D_
height: 100%;_x000D_
width: 100%;_x000D_
display: flex;_x000D_
position: fixed;_x000D_
align-items: center;_x000D_
justify-content: center;_x000D_
}
_x000D_
<div class="container">_x000D_
<div>centered text!</div>_x000D_
</div>
_x000D_