Vertical middle align
/*
Here first set the element position relative so we can set its position thought top and left.
Then set top 50% so element position set his parent height of 50%. Now we only need to minus
element half height as defined above minus margin but in margin method we need to define height
of the element.
*/
.selector {
position: relative;
top: 50%;
transform: translateY(-50%);
}