<div class="table">
    <div class="row">
        <div class="cell">
        <p>Blah blah</p>
        </div>
        <div class="cell">
        <p>Blah blah</p>
        </div>
        <div class="cell">
        <p>Blah blah</p>
        </div>
    </div>
</div>

.table {
    display: table;
    width: 100%;
}

.row {
    display: table-row;
    border-bottom: 1px solid black;
}

.cell {
    display: table-cell;
    width: 33%;
}
 

http://stackoverflow.com/questions/5542418/div-table-row-border/5542561

http://www.frontopen.com/331.html

http://www.runoob.com/xslfo/obj-table-row.html