.dad {
position: relative;
}
.son {
position: absolute;
margin: auto;
top: 0;
right: 0;
bottom: 0;
left: 0;
}
.dad {
position: relative;
}
.son {
width: 100px;
height: 100px;
position: absolute;
top: 50%;
left: 50%;
margin-top: -50px;
margin-left: -50px;
}
TODO...