if (document.images) {
    img1on = new Image();
    img1on.src = "./img/bizhub_entrance_img_e_on.jpg";

    img1off = new Image();
    img1off.src = "./img/bizhub_entrance_img_e.jpg";
}

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

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