body {
    background-color: #181818;
}
.xcenter {
    margin: auto;
    width: 50%;
    border: 3px solid red;
    background-color: lightgray;
    padding: 10px;
}

.center {
    width: 50%;
    height: 50%;
    overflow: auto;
    margin: auto;
    position: absolute;
    top: 0; left: 0; bottom: 0; right: 0;
    border: 6px solid rgba(223, 60, 60, 0.822);
    background-color: #6B728E;
  }
.img_center {
    display: block;
    margin-left: auto;
    margin-right: auto;
    width: 50%;
  }