function newImage(arg) {
  if (document.images) {
    rslt = new Image();
    rslt.src = arg;
    return rslt;
  }
}

function changeImages() {
  if (document.images && (preloadFlag == true)) {
    for (var i=0; i<changeImages.arguments.length; i+=2) {
      document[changeImages.arguments[i]].src = changeImages.arguments[i+1];
    }
  }
}

var preloadFlag = false;
function preloadImages() {
  if (document.images) {
    apropos_over = newImage("images/entree/apropos_over.gif");
    plan_over = newImage("images/entree/plan_over.gif");
    contact_over = newImage("images/entree/contact_over.gif");
    bt_entreprise_over = newImage("images/entree/bt_entreprise_over.gif");
    bt_particuliers_over = newImage("images/entree/bt_particuliers_over.gif");
    bt_remplacement_over = newImage("images/entree/bt_remplacement_over.gif");
    bt_santevoyage_over = newImage("images/entree/bt_santevoyage_over.gif");
    preloadFlag = true;
  }
}