Kanboard-Prod/assets/css/popover.css

/* popover */
#popover-container {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.8);
}

#popover-content {
    position: fixed;
    width: 70%;
    margin: 0 0 0 -35%;
    left: 50%;
    top: 5%;
    padding: 15px;
    background: #fff;
}