.error{
    background-color: #BC1010;
    padding: 6px 12px;
    border-radius: 4px;
    color: white;
    font-weight: bold;
    margin-left: 16px;
    margin-top: 6px;
    position: absolute;
}
.error:before{ /* Este es un truco para crear una flechita */
    content: '';
    border-top: 8px solid transparent;
    border-bottom: 8px solid transparent;
    border-right: 8px solid #BC1010;
    border-left: 8px solid transparent;
    left: -16px;
    position: absolute;
    top: 5px;
}