function MM_openBrWindow(theURL,winName,h,features) { 
  var l = 500; // largeur de la popup
  var h = 500; // largeur de la popup
  var PosX = ( screen.availWidth - l ) / 2; 
  var PosY = ( screen.availHeight - h ) / 2; 
  var features = "resizable=yes,scrollbars=yes,top="+PosY+",left="+PosX+",width="+l+",height="+h;
  window.open(theURL,winName,features); 
}