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) {
    home_over = newImage("common/home-on.gif");
    airport_over = newImage("common/airport-service-on.gif");
    corporate_over = newImage("common/corporate-on.gif");
    events_over = newImage("common/special-events-on.gif");
    contact_over = newImage("common/contact-on.gif");
    airline_over = newImage("common/airline-info-on.gif");
    traffic_over = newImage("common/traffic-info-on.gif");
    preloadFlag = true;
  }
}