.contenido {
    width: 700px;
    height: 200px;
    font-family: arial;
    font-size: 14px;
    padding: 10px;
    border: 1px solid red;
    margin: auto;
}

h1 {
    font-size: 25px;
    border-bottom: 1px solid red;
}

p {
    
}

.volver {
    color: #21B6A5;
    text-decoration: none;
    font-weight: bold;
    font-size: 18px;
    float: right;
}

.bordes-redondeados {
    
    -moz-border-radius: 5px;
    -webkit-border-radius: 5px;   
    border-radius: 5px;   
}