if (document.images) {

  image1on = new Image();
  image1on.src = "images/nav/home-on.jpg";
  
  image2on = new Image();
  image2on.src = "images/nav/project-narrative-on.jpg";

  image3on = new Image();
  image3on.src = "images/nav/pricing-information-on.jpg";

  image4on = new Image();
  image4on.src = "images/nav/contact-on.jpg";

  image5on = new Image();
  image5on.src = "images/nav/fcp-office-suites-on.jpg";

  image1off = new Image();
  image1off.src = "images/nav/home-off.jpg";
  
  image2off = new Image();
  image2off.src = "images/nav/project-narrative-off.jpg";
  
  image3off = new Image();
  image3off.src = "images/nav/pricing-information-off.jpg";
  
  image4off = new Image();
  image4off.src = "images/nav/contact-off.jpg";
  
  image5off = new Image();
  image5off.src = "images/nav/fcp-office-suites-off.jpg";
  
}
function turnOn(imageName) {
  if (document.images) {
    document[imageName].src = eval(imageName + "on.src");
  }
}

function turnOff(imageName) {
  if (document.images) {
    document[imageName].src = eval(imageName + "off.src");
  }
}