I took your advice though and searched "easing". Found a great site here...... About 4/5ths down the page is some script for an "opacity tween" that fades to transparent and would be a fantastic effect when something's added to cart.
Would you be able to offer any advice how I can apply the following script to the .messageStackSuccess?? I mean, what file would I have to attache the script to?? Would it be includes/classes/message_stack.php by any chance?
[div id="square33" style="width:50px;height:50px;background-color:#FF0000;filter:Alpha(opacity=100);"][/div]
[input type="button" value="change Opacity (100 - 0)" onClick="
opacityTween = new OpacityTween(document.getElementById('square33'),Tween.bounceEaseOut, 100, 0, 3);
$this->messages = array('params' => 'class="messageStackSuccess larger"', 'class' => $class, 'text' => zen_image($template->get_template_dir(ICON_IMAGE_SUCCESS, DIR_WS_TEMPLATE, $current_page_base,'images/icons'). '/' . ICON_IMAGE_SUCCESS, ICON_SUCCESS_ALT) . ' ' . $message);