Tu n'a pas refermé ton else ...
else
{
// On enregistre dans la base de données //
mysql_connect("borgniet.sql.jexiste.be","borgniet","u3e6zvnf");
mysql_select_db("borgniet");
$societe = htmlentities($_POST['societe'], ENT_QUOTES);
$civilite = htmlentities($_POST['civilite'], ENT_QUOTES);
$nom = htmlentities($_POST['nom'], ENT_QUOTES);
$prenom = htmlentities($_POST['prenom'], ENT_QUOTES);
$fonction = htmlentities($_POST['fonction'], ENT_QUOTES);
$adresse = htmlentities($_POST['adresse'], ENT_QUOTES);
$cp = htmlentities($_POST['CP'], ENT_QUOTES);
$localite = htmlentities($_POST['localite'], ENT_QUOTES);
$mail = htmlentities($_POST['mail'], ENT_QUOTES);
$message = htmlentities($_POST['message'], ENT_QUOTES);
$message = nl2br($message);
$telephone = htmlentities($_POST['telephone'], ENT_QUOTES);
mysql_query("INSERT INTO messages VALUES('',' " . $societe . " ' , ' " . $civilite . " ' , ' " . $nom . " ' , ' " . $prenom . " ' , ' " . $fonction . " ' , ' " . $adresse . " ' , ' " . $cp . " ' , ' " . $localite . " ' , ' " . $mail . " ' , ' " . $message . " ' , ' " . $telephone . " ' , '')");
}
?>