.parent {
width: 200px;
height: 200px;
background-color: black;
}
.child {
position: relative;
height: 100px;
width: 100px;
top: 50%;
left: 50%;
background-color:red;
-webkit-transform: translateX(-50%) translateY(-50%);
-moz-transform: translateX(-50%) translateY(-50%);
-o-transform: translateX(-50%) translateY(-50%);
-ms-transform: translateX(-50%) translateY(-50%);
transform: translateX(-50%) translateY(-50%);
}
