.position-absolute-xy-center{
    position: absolute;
    top: 50%;
    left: 50%;
    -webkit-transform:translate(-50%, -50%);
       -moz-transform:translate(-50%, -50%);
        -ms-transform:translate(-50%, -50%);
         -o-transform:translate(-50%, -50%);
            transform:translate(-50%, -50%);
}




.position-fixed-xy-center{
    position: fixed;
    top: 50%;
    left: 50%;
    -webkit-transform:translate(-50%, -50%);
       -moz-transform:translate(-50%, -50%);
        -ms-transform:translate(-50%, -50%);
         -o-transform:translate(-50%, -50%);
            transform:translate(-50%, -50%);
}