You might have picked up on a theme in this chapter: While implementing your own navigational enhancements is cool, it almost always makes more sense to rely on a third-party library for non-trivial scripts. The amount of testing and cross-browser tweaking necessary to get complex DHTML functionality working on a variety of platforms and browsers is staggering, so if at all possible, let someone else do the work for you.
There are many libraries on the Web that you can use. They are usually very well tested, and accommodate browsers most developers don’t have easy access to for testing (e.g., old versions of IE, Safari, IE for Macintosh, Netscape 4 on Solaris, obscure open-source browsers, and so on). We cannot emphasize enough how much of a time-saving device third-party DHTML packages can be. Even the authors use them unless we have some compelling reason not to.