<div class="parent">
<div class="child"></div>
</div>
.parent {
position: relative;
width: 200px;
height: 200px;
border: 1px solid;
}
.child {
position: absolute;
top: 0;
right: 0;
bottom: 0;
left: 0;
width: 50%;
height: 50%;
margin: auto;
background-color: #699;
}