MediaWiki:Common.css

/* CSS placed here will be applied to all skins */
table {
   border-collapse: collapse;
   padding: 1em 0 1em 0;
   border: 1px solid black;
}

table td,table th {
   border: 1px solid black;
   text-align: center;
}

.strongDivider {
   border-top: 3px solid black;
}

table.borderless td {
   border-top-style: none;
   border-bottom-style: none;
}

tr.divider {
    border-top: 1px solid black;
}