The Extensions Manager lets you install, configure, and uninstall add-ons at will. (Click on image to expand.)

Pros: Not only is it easy for you to customize Firefox, it's very easy for other people to have an idea about how to improve the browser and then make it available to everyone for free. In fact, Firefox was designed from the ground up to accept third-party skins, called Themes, and third-party browser add-ons of all sorts, called Extensions. Firefox's Tools menu gives you access to Extensions and Themes Web sites that provide lists of these browser upgrades and an easy way of installing them.

At press time, there were 55 Firefox themes available, each of which offers a different look and feel of the browser. There were also approaching 150 Firefox extensions, many of which are small (under 100K) modifications or tweaks to the interface that provide some new bit of functionality or control. You're very likely to find at least of couple of Firefox extensions that interest you. If this browser rises in popularity, as well it might, expect to see a lot more extensions. It's a powerful aspect of Firefox that should leverage the nature of the open-source community.

Of course, Internet Explorer supports ActiveX controls, Browser Help Objects, and toolbars. And many of these have been developed over the years. (In fact, Microsoft offers its Windows Marketplace of third-party IE customizations and add-ons.) But ActiveX controls have become as much a liability to IE as they've been a help because of security issues. Firefox could face the same problem. Although Mozilla is marketing the product as a safer browser than IE, that's not technically accurate. If Firefox's market share grows significantly, you can expect that its vulnerabilities, whatever they are (and every software program has them), will be tested as well.

Firefox provides characteristically simplistic tools for managing themes and extensions. Until the version of IE6 found in Windows XP SP2, Internet Explorer didn't even provide a user interface for managing third-party browser add-ons. The Firefox Extensions tool offers the basics: A link to the Mozilla site where you can browse for new extensions, an Uninstall button, an Update button, and an Options button. It's what you need, nothing more. The Themes tool is very similar.

Cons: The only shortcoming of the Extensions functionality is that so far it doesn't seem to be updated very frequently. Many of the extensions that were available in pre-releases of Firefox have updated versions for Firefox 1.0, but they aren't shown as being available from Mozilla's site. You need to surf over to the home pages for each extension and find the newer versions, if available. Mozilla, please keep this as up-to-date as possible.