if (document.images) {            // Active Images
            hochon = new Image();
            hochon.src = "../_img/hoch_1.jpg";
            backon = new Image();
            backon.src = "../_img/back_1.jpg";
            nexton = new Image();
            nexton.src = "../_img/next_1.jpg";

            hochoff = new Image();
            hochoff.src = "../_img/hoch_0.jpg";
            backoff = new Image();
            backoff.src = "../_img/back_0.jpg";
            nextoff = new Image();
            nextoff.src = "../_img/next_0.jpg";
        }

// 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");
        }
}