if (document.images) {
    var image_array = new Array();

    // path to the directory with images
    var path = 'images/';

    // enumeration of the "active" images
    image_array[0] = path + "index_01_02.jpg";
    image_array[1] = path + "index_02_02.jpg";
    image_array[2] = path + "index_03_02.jpg";
    image_array[3] = path + "index_04_02.jpg";

    var preload_image = new Array();

    for (var i = 0; i < image_array.length; i++) {
        preload_image[i] = new Image();
        preload_image[i].src = image_array[i];
    }
}

function rollover(name, filename) {
    var fullpath = 'images/' + filename;
    document.images[name].src = fullpath;
}