if (document.images)   {
     image1on = new Image();
     image1on.src="img/nav1b.jpg";

     image1off = new Image();
     image1off.src = "img/nav1a.jpg";

}

if (document.images)   {
     image2on = new Image();
     image2on.src="img/nav2b.jpg";

     image2off = new Image();
     image2off.src = "img/nav2a.jpg";

}

if (document.images)   {
     image3on = new Image();
     image3on.src="img/nav3b.jpg";

     image3off = new Image();
     image3off.src = "img/nav3a.jpg";

}

if (document.images)   {
     image4on = new Image();
     image4on.src="img/nav4b.jpg";

     image4off = new Image();
     image4off.src = "img/nav4a.jpg";

}

if (document.images)   {
     image5on = new Image();
     image5on.src="img/nav5b.jpg";

     image5off = new Image();
     image5off.src = "img/nav5a.jpg";

}

if (document.images)   {
     image6on = new Image();
     image6on.src="img/nav6b.jpg";

     image6off = new Image();
     image6off.src = "img/nav6a.jpg";

}

if (document.images)   {
     image7on = new Image();
     image7on.src="img/nav7b.jpg";

     image7off = new Image();
     image7off.src = "img/nav7a.jpg";

}

if (document.images)   {
     image8on = new Image();
     image8on.src="img/nav8b.jpg";

     image8off = new Image();
     image8off.src = "img/nav8a.jpg";

}

if (document.images)   {
     image9on = new Image();
     image9on.src="img/nav9b.jpg";

     image9off = new Image();
     image9off.src = "img/nav9a.jpg";

}

if (document.images)   {
     image10on = new Image();
     image10on.src="img/nav10b.jpg";

     image10off = new Image();
     image10off.src = "img/nav10a.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");
     }
}