div.description {
    padding: 0 0 1em 1em;
}

table.notebook {
    border-collapse: collapse;
}

table.notebook th {
    padding: 0 1em 0 1em;
    border-bottom: 1px solid black;
}

table.notebook td {
    padding: .5em 1em 0 1em; 
    border-bottom: 1px solid lightgrey;
}