.marco {
    width:500px;
    border:solid blue 1px;
    margin:10px auto;
    }
    
.marco  .cabecera {
    background-color: rgba(100,100,150,0.7);
    color:white;
    padding:16px;
}

.marco  .cuerpo {
    padding:20px;
    background-color:rgba(255,255,255,0.7);
}

.marco  .pie {
    background-color:rgba(100,100,150,0.8);
    text-align:center;
    font-size:10px;
    color:white;
    padding:8px;
}