Posición de centro absoluto
.child {
position: absolute;
top: 50%;
left: 50%;
transform: translate(-50%, -50%);
}
Grieving Gemsbok
.child {
position: absolute;
top: 50%;
left: 50%;
transform: translate(-50%, -50%);
}#child {
position: absolute;
width: 70px;
height: 70px;
background-color: blue;
left: 50%;
top: 50%;
border-radius: 50%;
transform: translate(-50%, -50%);
}position: absolute;
margin-left: auto;
margin-right: auto;
left: 0;
right: 0;
text-align: center;