addcart_img_out = new Image();
addcart_img_out.src = "images/cart/add_to_cart.png";
addcart_img_out.alt = 'Add to cart';
addcart_img_over = new Image();
addcart_img_over.src = "images/cart/add_to_cart_over.png";
addcart_img_over.alt = 'Add to cart';
checkout_img_out = new Image();
checkout_img_out.src = "images/cart/checkout_small.png";
checkout_img_out.alt = 'Add to cart';
checkout_img_over = new Image();
checkout_img_over.src = "images/cart/checkout_small_over.png";
checkout_img_over.alt = 'Add to cart';

function addcart_display(imgName, imgUrl) {
    if (document.images && typeof imgUrl != 'undefined') {
        document[imgName].src = imgUrl.src;
        document[imgName].alt = 'Add to cart';
    }
}

function checkout_display(imgName, imgUrl) {
    if (document.images && typeof imgUrl != 'undefined') {
        document[imgName].src = imgUrl.src;
        document[imgName].alt = 'Add to cart';
    }
}