<table>
<tr>
<td></td><td></td>
</tr>
........................
</table>

//Массив в 101 элемент
$arr = range(0,100);

echo '<table><tr><td>';

$i = -1;

foreach($arr as $key=>$value)
{   
    $i++;
    if($i%13==0)
        echo '</tr><tr>';
        
    echo '<td>'.$value.'';
}

echo '</td></tr></table>';

0	1	2	3	4	5	6	7	8	9	10	11	12
13	14	15	16	17	18	19	20	21	22	23	24	25
26	27	28	29	30	31	32	33	34	35	36	37	38
39	40	41	42	43	44	45	46	47	48	49	50	51
52	53	54	55	56	57	58	59	60	61	62	63	64
65	66	67	68	69	70	71	72	73	74	75	76	77
78	79	80	81	82	83	84	85	86	87	88	89	90
91	92	93	94	95	96	97	98	99	100

echo "<div class=\"index_cat gray sm\">"; 
echo'<table border="1"><tr><td>';
while($category = mysql_fetch_assoc($categories)){
        $name_cat = (defined('JBLANG') && constant('JBLANG')=='en') ? $category['en_name_cat'] : $category['name_cat'];
        echo (@$category['img'])?"<img alt=\"".$name_cat."\" class=\"rootcatimg\" src=\"".$u."cat/".$category['img']."\" />":"";
        if($category['child_category']==1){
                echo "<span class=\"rootcat\">".$name_cat."</span><br />";
                listcat2($category['id'],1);
                echo "<br />";
        }else{
                $count_ads = mysql_result(mysql_query("SELECT COUNT(id) from jb_board WHERE id_category='".$category['id']."' AND old_mess='old'".$GLOBALS['subQuery']), 0);cq();
                echo "<a href=\"c".$category['id'].".html\">".$name_cat."</a> (".@$count_ads.")<br />";
        }
}
echo'</td></tr></table>';
echo "</div><div class=\"clear\"></div>";

$i=0;
while($category = mysql_fetch_assoc($categories)){
        $name_cat = (defined('JBLANG') && constant('JBLANG')=='en') ? $category['en_name_cat'] : $category['name_cat'];
        echo (@$category['img'])?"<img alt=\"".$name_cat."\" class=\"rootcatimg\" src=\"".$u."cat/".$category['img']."\" />":"";
        if($category['child_category']==1){
                echo "<span class=\"rootcat\">".$name_cat."</span><br />";
                listcat2($category['id'],1);
                echo "<br />";
        }else{
                $count_ads = mysql_result(mysql_query("SELECT COUNT(id) from jb_board WHERE id_category='".$category['id']."' AND old_mess='old'".$GLOBALS['subQuery']), 0);cq();
                echo "<a href=\"c".$category['id'].".html\">".$name_cat."</a> (".@$count_ads.")<br />";
        }
if ($i==50)echo'</td><td>';
$i++;}

echo "<div class=\"index_cat gray sm\">"; 
echo'<table border="1"><tr><td>';
$i=0;
while($category = mysql_fetch_assoc($categories)){
        $name_cat = (defined('JBLANG') && constant('JBLANG')=='en') ? $category['en_name_cat'] : $category['name_cat'];
        echo (@$category['img'])?"<img alt=\"".$name_cat."\" class=\"rootcatimg\" src=\"".$u."cat/".$category['img']."\" />":"";
        if($category['child_category']==1){
                echo "<span class=\"rootcat\">".$name_cat."</span><br />";
                listcat2($category['id'],1);
                echo "<br />";
        }else{
                $count_ads = mysql_result(mysql_query("SELECT COUNT(id) from jb_board WHERE id_category='".$category['id']."' AND old_mess='old'".$GLOBALS['subQuery']), 0);cq();
                echo "<a href=\"c".$category['id'].".html\">".$name_cat."</a> (".@$count_ads.")<br />";
        }
if ($i==50)echo'</td><td>';
$i++;}
echo'</td></tr></table>';
echo "</div><div class=\"clear\"></div>";

echo "<div class=\"index_cat gray sm\">"; 
echo'<table border="1"><tr><td>';
$i=0;
while($category = mysql_fetch_assoc($categories))
    {
        $name_cat = (defined('JBLANG') && constant('JBLANG')=='en') ? $category['en_name_cat'] : $category['name_cat'];
        echo (@$category['img'])?"<img alt=\"".$name_cat."\" class=\"rootcatimg\" src=\"".$u."cat/".$category['img']."\" />":"";
        if($category['child_category']==1){
            echo "<span class=\"rootcat\">".$name_cat."</span><br />";
            listcat2($category['id'],1);
            echo "<br />";
        }else{
                  // Проверяем, количество строк и добавляем столбец в случае чего.... begin
                 if ( $i == 50 )
                    {
                       echo '</td><td>';
                       $i = 0; // Обнуляем счетчик
                    }
                 else
                    $i++;
                 // Проверяем, количество строк и добавляем столбец в случае чего.... end
			
            $count_ads = mysql_result(mysql_query("SELECT COUNT(id) from jb_board WHERE id_category='".$category['id']."' AND old_mess='old'".$GLOBALS['subQuery']), 0);cq();
            echo "<a href=\"c".$category['id'].".html\">".$name_cat."</a> (".@$count_ads.")<br />";
        }
    }
echo'</td></tr></table>';
echo "</div><div class=\"clear\"></div>";

$i = 0; // Обнуляем счетчик

$i = 1; // Обнуляем счетчик