if (document.images) {
  about = new Image();
  about.src = "/images/nav/about.gif";
  about_on = new Image();
  about_on.src = "/images/nav/about_on.gif";
  
  services = new Image();
  services.src = "/images/nav/services.gif";
  services_on = new Image();
  services_on.src = "/images/nav/services_on.gif";
  
  help = new Image();
  help.src = "/images/nav/help.gif";
  help_on = new Image();
  help_on.src = "/images/nav/help_on.gif";
  
  newsletter = new Image();
  newsletter.src = "/images/nav/newsletter.gif";
  newsletter_on = new Image();
  newsletter_on.src = "/images/nav/newsletter_on.gif";
  
  news_and_events = new Image();
  news_and_events.src = "/images/nav/news_and_events.gif";
  news_and_events_on = new Image();
  news_and_events_on.src = "/images/nav/news_and_events_on.gif";
  
  contact = new Image();
  contact.src = "/images/nav/contact.gif";
  contact_on = new Image();
  contact_on.src = "/images/nav/contact_on.gif";
  
  newsletter = new Image();
  newsletter.src = "/images/nav/newsletter.gif";
  newsletter_on = new Image();
  newsletter_on.src = "/images/nav/newsletter_on.gif";
  
}

function switchOn(imgName) {
    if (document.images) {
      document[imgName].src = eval(imgName + "_on.src");
    }
}
  
function switchOff(imgName) {
    if (document.images) {
      document[imgName].src = eval(imgName + ".src");
    }
}