if (document.images) {

// STANDARD GIFS
    img1off = new Image();
    img1off.src = "img/nav_home_01.gif";
    img2off = new Image();
    img2off.src = "img/nav_about_01.gif";
    img3off = new Image();
    img3off.src = "img/nav_teachers_01.gif";
    img4off = new Image();
    img4off.src = "img/nav_courses_01.gif";
    img5off = new Image();
    img5off.src = "img/nav_location_01.gif";
    img6off = new Image();
    img6off.src = "img/nav_timetable_01.gif";
    img7off = new Image();
    img7off.src = "img/nav_contact_01.gif";
    img8off = new Image();
    img8off.src = "img/nav_faq_01.gif";

// ROLLOVER GIFS
    img1on = new Image();
    img1on.src = "img/nav_home_02.gif";
    img2on = new Image();
    img2on.src = "img/nav_about_02.gif";
    img3on = new Image();
    img3on.src = "img/nav_teachers_02.gif";
    img4on = new Image();
    img4on.src = "img/nav_courses_02.gif";
    img5on = new Image();
    img5on.src = "img/nav_location_02.gif";
    img6on = new Image();
    img6on.src = "img/nav_timetable_02.gif";
    img7on = new Image();
    img7on.src = "img/nav_contact_02.gif";
    img8on = new Image();
    img8on.src = "img/nav_faq_02.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");
        }
}