label.error {
    background: red;
    padding: 5px;
    color: #FFF;
}

.signature {
    border: 1px solid #ccc;
    border-radius: 4px;
    overflow: hidden;
    position: relative;
}
.undo {
    position: absolute;
    top: 5px;
    right: 5px;
}
.signature_field {
    visibility: hidden;
    width: 0; margin: 0; padding: 0; border: 0;
}