Fejl i counter..

Hey..
KAN I FINDE DENNE FEJL:
Warning: Division by zero in /web/www/frac/users/madsass/Andet/stats/counter_admin.php on line 51

I DETTE STYKKE:
echo "$spacer";
$result = mysql_query("SELECT * FROM counthits WHERE start like 'no' AND FROM_UNIXTIME(time, '%d%m%Y') not like '$date_today'");
$amount = mysql_num_rows($result);
$result = mysql_query("SELECT SUM(userstoday) as sum FROM counthits WHERE start like 'no' AND FROM_UNIXTIME(time, '%d%m%Y') not like '$date_today'");
$row = mysql_fetch_array($result);
$hits = ceil($row[sum]/$amount);
echo "$hits pr dag";
echo "$spacer";

Med Venlig Hilsen
Madsass