You can use the box-shadowbox-shadow property to "fake"fake a border of tra tr element. Adjust Y position of box-shadowbox-shadow (below represented as 2px) to adjust thickness.
tr { -webkit-box-shadow: 0px 2px 0px 0px rgba(0,0,0,0.99); -moz-box-shadow: 0px 2px 0px 0px rgba(0,0,0,0.99); box-shadow: 0px 2px 0px 0px rgba(0,0,0,0.99); }