Vertically/Horizontal center a content block:

csstips.css

(IE9+)
.center-horizontal {
    position: relative;
    left: 50%;
    transform: translateX(-50%); 
}

.center-vertical {
    position: relative;
    top: 50%;
    transform: translateY(-50%); 
}

.abs-center {
    position: absolute;
    top: 50%;
    left: 50%;
    transform:translate(-50%,-%50);
}