if(document.images)
{
		techniques_img = new Image;
		techniques_img = "<?php echo $chemin ?>img/bt_techniques-over.gif";
		fondements_img = new Image;
		fondements_img = "<?php echo $chemin ?>img/bt_fondements-over.gif";
		usages_img = new Image;
		usages_img = "<?php echo $chemin ?>img/bt_usages-over.gif";
		ethique_img = new Image;
		ethique_img = "<?php echo $chemin ?>img/bt_ethique-over.gif";
}