photos = new Image();
photos.src = "images/photos-off.gif";
mission = new Image();
mission.src = "images/mission-off.gif";
about = new Image();
about.src = "images/about-off.gif";
founders = new Image();
founders.src = "images/founders-off.gif";
sponsor = new Image();
sponsor.src = "images/sponsor-off.gif";
contact = new Image();
contact.src = "images/contact-off.gif";
tour = new Image();
tour.src = "images/tourlogo.jpg";

photoson = new Image();
photoson.src = "images/photos-on.gif";
missionon = new Image();
missionon.src = "images/mission-on.gif";
abouton = new Image();
abouton.src = "images/about-on.gif";
founderson = new Image();
founderson.src = "images/founders-on.gif";
sponsoron = new Image();
sponsoron.src = "images/sponsor-on.gif";
contacton = new Image();
contacton.src = "images/contact-on.gif";
touron = new Image();
touron.src = "images/tourlogo-on.jpg";

function on(imgName){
  document.images[imgName].src = eval(imgName+'on.src');
}

function off(imgName){
  document.images[imgName].src = eval(imgName+'.src');
}