Posição central fixa
.centered {
position: fixed;
top: 50%;
left: 50%;
transform: translate(-50%, -50%);
}
Emil Rauhe
.centered {
position: fixed;
top: 50%;
left: 50%;
transform: translate(-50%, -50%);
}position: fixed;
width: 500px;
height: 200px;
margin: 5% auto; /* Will not center vertically and won't work in IE6/7. */
left: 0;
right: 0;