function popup_ventes(){
	var opts = 'scrollbars=yes,resizable=no,menubar=yes,status=no';
	var w = 500;
	var h = 500;
	var t = (screen.height - h)/2;
	var l = (screen.width - w)/2;
	var pw = window.open('popup_ventes.php','','width='+w+',height='+h+',top=50,left='+l+','+opts);
}