//standard image

    img0off = new Image();
    img0off.src = "img/nav0a.gif";
    img1off = new Image();
    img1off.src = "img/nav1a.gif";
    img2off = new Image();
    img2off.src = "img/nav2a.gif";
    img3off = new Image();
    img3off.src = "img/nav3a.gif";
    img4off = new Image();
    img4off.src = "img/nav4a.gif";
    img5off = new Image();
    img5off.src = "img/nav5a.gif";
    img6off = new Image();
    img6off.src = "img/nav6a.gif";
    img7off = new Image();
    img7off.src = "img/nav7a.gif";
    img8off = new Image();
    img8off.src = "img/nav8a.gif";
    img9off = new Image();
    img9off.src = "img/nav9a.gif";
    img10off = new Image();
    img10off.src = "img/nav10a.gif";
    img11off = new Image();
    img11off.src = "img/nav11a.gif";
    img12off = new Image();
    img12off.src = "img/nav12a.gif";
    img13off = new Image();
    img13off.src = "img/nav13a.gif";

//on rollover image

if (document.images) {

    img0on = new Image();
    img0on.src = "img/nav0b.gif";
    img1on = new Image();
    img1on.src = "img/nav1b.gif";
    img2on = new Image();
    img2on.src = "img/nav2b.gif";
    img3on = new Image();
    img3on.src = "img/nav3b.gif";
    img4on = new Image();
    img4on.src = "img/nav4b.gif";
    img5on = new Image();
    img5on.src = "img/nav5b.gif";
    img6on = new Image();
    img6on.src = "img/nav6b.gif";
    img7on = new Image();
    img7on.src = "img/nav7b.gif";
    img8on = new Image();
    img8on.src = "img/nav8b.gif";
    img9on = new Image();
    img9on.src = "img/nav9b.gif";
    img10on = new Image();
    img10on.src = "img/nav10b.gif";
    img11on = new Image();
    img11on.src = "img/nav11b.gif";
    img12on = new Image();
    img12on.src = "img/nav12b.gif";
    img13on = new Image();
    img13on.src = "img/nav13b.gif";

}

// Function to 'activate' images.
function imgOn(imgName) {
        if (document.images) {
            document[imgName].src = eval(imgName + "on.src");
        }
}

// Function to 'deactivate' images.
function imgOff(imgName) {
        if (document.images) {
            document[imgName].src = eval(imgName + "off.src");
        }
}