CSS:
    table.tblcl { border-collapse: collapse;
                  border-width: 1px 1px 1px 1px;
                  border-spacing: 1px;
                  border-style: none none none none; }
    table.tblcl td { border-width: 1px 1px 1px 1px;
                     padding: 1px 1px 1px 1px;
                     border-style: dotted dotted dotted dotted;
                     -moz-border-radius: 0px 0px 0px 0px; }
    table.tblclh td { border-width: 0px 0px 0px 0px;
                      padding: 1px 1px 1px 1px;
                      border-style: hidden hidden hidden hidden;
                      -moz-border-radius: 0px 0px 0px 0px; }


Code:
<table class="tblcl">

Normal rows, with border:
 echo "<TR><TD colspan=85 class='wd'> " . $Sub[$i] . " </TD>\n";
        $a = 1;
        While ($Range[$a][0] <> "") {

            // absence
            if ($Abs[$Sub[$i]][$Range[$a][0]] <> "")
                echo "<TD class='absr' title='" . $Range[$a][0] . "'>&nbsp;&nbsp;</TD>\n";

Rows that i want to have no border:
echo "<td class='tblclh'>";
    if ($i != 0 && ($i % 10 == 0)) print $i / 10;
    else echo "&nbsp;";