Remova a linha:
$row = mysql_fetch_array($result);
O
while loop irá pegar a primeira linha na primeira iteração. Código resultante:
<?php
$ordre = "nom";
$croissance = "ASC";
if(isset($_GET["ordre"])){
$ordre = $_GET["ordre"];
};
if(isset($_GET["croissance"])){
$croissance = $_GET["croissance"];
};
$con = mysql_connect('localhost','root','');
mysql_select_db('sdj_jeux', $con);
$sql = "SELECT * FROM jeux ORDER BY $ordre $croissance";
$result = mysql_query($sql, $con);
$couleurcompteur = 0;
while ($row = mysql_fetch_array($result)){
$couleurcompteur += 1;
if($couleurcompteur % 2){
$classe = "pale";
} else {
$classe = "fonce";
};
?>
