centering with flex

center.css

    
    display: -webkit-box;
    display: -moz-box;
    display: -webkit-flex;
    display: flex;
    -webkit-flex-direction: row;
    flex-direction: row;
    -webkit-flex-wrap: wrap;
    flex-wrap: wrap;
    -webkit-box-pack: center;
    -moz-box-pack: center;
    -webkit-justify-content: center;
    justify-content: center;
    -webkit-box-align: center;
    -moz-box-align: center;
    -webkit-align-items: center;
    align-items: center;