Most HTML tags can be used in the long description. Just be careful when adding scripts, as they could conflict with the cart itself. If you run into a problem, simply remove the scripts and/or code and reupload your cart.
Tip: Use Photo Gallery, Web JukeBox, or Web Video Player to enhance your product description! For more information about adding Flash elements to your description or custom pages, read this article: Adding Flash Elements to Shopping Cart Creator.