if (document.images) {
port4a = new Image;
port4b = new Image;
port4c = new Image;
port4a.src = 'images/port4_a.jpg';
port4b.src = 'images/port4_b.jpg';
port4c.src = 'images/port4_c.jpg';
} else {
port4a = '';
port4b = '';
port4c = '';
document.rollimg = '';
}