body {
    margin: 0px;
    background-color: #bbb;
}

div#main {
    position: absolute;
    left: 50%;
    top: 50%;

    transform: translate(-50%, -50%);

    background-color: #eee;

    padding: 14px 20px;

    width: 400px;

    border: 4px solid black;
}

p#errorLabel {
    color: red;
}

p#successLabel {
    color: green;
}