<rich:dataTable>
has rowClass
attribute, if you want lines between rows you can make a CSS class like this one:
.row-line {
border-bottom: 2px solid black;
}
EDIT:
The first row in a dataTable has the rf-dt-fst-r
class. So in case you'd want to add a line above the table:
.row-line.rf-dt-fst-r {
border-top: 2px solid black;
}