if (document.images) {
  
  homeon = new Image();
  homeon.src = "images/home_on.gif";
  homeoff = new Image();
  homeoff.src = "images/home_off.gif";
  
  abouton = new Image();
  abouton.src = "images/about_on.gif";
  aboutoff = new Image();
  aboutoff.src = "images/about_off.gif";
  
  contacton = new Image();
  contacton.src = "images/contact_on.gif";
  contactoff = new Image();
  contactoff.src = "images/contact_off.gif";
  
  productson = new Image();
  productson.src = "images/cds_on.gif";
  productsoff = new Image();
  productsoff.src = "images/cds_off.gif";
  }

function turnOn(imageName) {
  if (document.images && document.images[imageName]) {
    document.images[imageName].src = eval(imageName + "on.src");
  }
}

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

function launchURL(mypage, myname, w, h, s) {
var winl = (screen.width - w) / 2;
var wint = (screen.height - h) / 3;
winprops = 'height='+h+',width='+w+',top='+wint+',left='+winl+',scrollbars='+s;
win = window.open(mypage, myname, winprops);
}