Warning: mysql_fetch_array() expects parameter 1 to be resource

<table  align="center" border="1" bordercolor="9c5959">
       <tr bgcolor="#9c5959">
   <td> <div align="center" class="Style11"><span class="Style12">Domaine</span></div></td>
   <td><div align="center" class="Style11"><span class="Style12">Thème</span></div></td>
            <td><div align="center" class="Style11"><span class="Style12">Animateur</span></div></td>
            <td><div align="center" class="Style11"><span class="Style12">Detail</span></div></td>
   
        </tr>
        <tr>
        <?php
$nom_dom="";
if(!empty($_POST['nom_dom'])) $nom_dom=$_POST['nom_dom'];



// Numero de page (1 par défaut)
if( isset($_GET['page']) && is_numeric($_GET['page']) )
 $page = $_GET['page'];
else
 $page = 1;

// Nombre d'info par page
$pagination = 10;
// Numéro du 1er enregistrement à lire
$limit_start = ($page - 1) * $pagination;

// Préparation de la requête
  include("config.php");
$sql = "SELECT * FROM conferences LIMIT $limit_start, $pagination";

// Requête SQL
//$res = mysql_query($sql);

// Traitement et affichage des données
//while ( $donnee = mysql_fetch_assoc($res) ) {


      
    
    
            if(!empty($nom_dom))
      
        $sql=$sql." and code_dom='$nom_dom'";
  $sql=$sql." order by code desc";
  $res= mysql_query($sql);
  $a=true;
  while($row= mysql_fetch_row($res)) 
        {
  
 // echo "<tr><td>$req</td><td>$row[1]</td> <td>$row[2]</td><td> $row[3]</td><td>Detail...</td>";
 
        echo "
  <td align=\"center\">$row[15]</td>
  <td align=\"center\">$row[1]</td>
  <td align=\"center\">$row[7]</td>
  ";


}

// Nb d'enregistrement total
$nb_total = mysql_query('SELECT COUNT(*) AS nb_total FROM conferences');
$nb_total = mysql_fetch_array($nb_total);
$nb_total = $nb_total['nb_total'];

// Pagination
$nb_pages = ceil($nb_total / $pagination);

echo '<p>[ Page :';
// Boucle sur les pages
for ($i = 1 ; $i <= $nb_pages ; $i++) {
 if ($i == $page )
  echo " $i";
 else
  echo " <a href=\"?page=$i\">$i</a> ";
}
echo ' ]</p>';


  

  
        ?>
        <td><a href="Detail_cof.php?code=<?php echo $row[0]; ?>" style="color:#000000" ><img src="images\detail.png" width="32px" height="32px"  style="margin-left:10px" alt="Detail"/></a></td></tr>
        <?php
        //}
        //pour fermer la chaine connexion
        mysql_close() or die("connexion deconnexion");
        ?>
         </table>
     

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