div.sm-popup.sm-tooltip.sm-popup-shadow {
    box-shadow: 0px 4px 15px 1px rgba(0,0,0,0.6);
    -webkit-box-shadow: 0px 4px 15px 1px rgba(0,0,0,0.6);
    -moz-box-shadow: 0px 4px 15px 1px rgba(0,0,0,0.6);
}