function preloadImages() {
  if (document.images) {

    aboutglynon = new Image(); 
    aboutglynon.src = "images/aboutglyn_navbutton_on.gif";
    aboutglynoff = new Image(); 
    aboutglynoff.src = "images/aboutglyn_navbutton_off.gif"; 

    propertieson = new Image(); 
    propertieson.src = "images/properties_navbutton_on.gif";
    propertiesoff = new Image(); 
    propertiesoff.src = "images/properties_navbutton_off.gif"; 

    mortgagecalculatorson = new Image(); 
    mortgagecalculatorson.src = "images/mortgagecalculators_navbutton_on.gif";
    mortgagecalculatorsoff = new Image(); 
    mortgagecalculatorsoff.src = "images/mortgagecalculators_navbutton_off.gif"; 

    homebuyerson = new Image(); 
    homebuyerson.src = "images/homebuyers_navbutton_on.gif";
    homebuyersoff = new Image(); 
    homebuyersoff.src = "images/homebuyers_navbutton_off.gif"; 

    homesellerson = new Image(); 
    homesellerson.src = "images/homesellers_navbutton_on.gif";
    homesellersoff = new Image(); 
    homesellersoff.src = "images/homesellers_navbutton_off.gif"; 

    medhaton = new Image(); 
    medhaton.src = "images/medhat_navbutton_on.gif";
    medhatoff = new Image(); 
    medhatoff.src = "images/medhat_navbutton_off.gif"; 

    contacton = new Image(); 
    contacton.src = "images/contact_navbutton_on.gif";
    contactoff = new Image(); 
    contactoff.src = "images/contact_navbutton_off.gif"; 

    homeon = new Image(); 
    homeon.src = "images/home_navbutton_on.gif";
    homeoff = new Image(); 
    homeoff.src = "images/home_navbutton_off.gif"; 

  }
}

function imgOn(imgName) {
  if (document.images) {
    document[imgName].src = "images/" + imgName + "_navbutton_on.gif";
  }
}

function imgOff(imgName) {
  if (document.images) {
    document[imgName].src = "images/" + imgName + "_navbutton_off.gif";
  }
}  

onLoad=preloadImages();