if (document.images) {
  swArray = [];
  swArray[0] = "on";
  swArray[1] = "off";
  var nameArray = [];
  nameArray[1] = "home";
  nameArray[2] = "about";
  nameArray[3] = "products";
  nameArray[4] = "services";
  nameArray[5] = "news";
  nameArray[6] = "contact";
  var ons = "_On"
  for(i=0;i<=1;i++) {
    for(j=1;j<=6;j++) {
      eval("img" + j + swArray[i] + " = new Image();")
      eval("img" + j + swArray[i] + ".src = 'images/" + nameArray[j] + ons + ".gif';");
    }
    ons = "";
  }
}

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");
  }
}