When you use the BORDER tag (see page 146), a border appears between each cell and also around the table itself. HTML 4 lets you choose which external sides of the table should have a border as well as which internal borders should be displayed.
To choose which external sides should have a border:
void, for no external borders
above, for a single border on top
below, for a single border on bottom
hsides, for a border on both the top and bottom sides
vsides, for a border on both the right and left sides
rhs, for a single border on the right side
lhs, for a single border on the left side
box or border, for a border on all sides (default)