to AkeL:
$sql = "SELECT u.email, u.icq, u.avatar, t.topics, t.user, t.date FROM $tab_user AS u LEFT JOIN $tab_topics AS t ON u.username=t.user";
$result = mysql_query($sql);
while($row = mysql_fetch_object($result))
echo "$row->user | $row->date | $row->topics | $row->icq | $row->email |...