As the window to the Internet, the Web browser is arguably the most important application ever developed, and it will only become more important in the coming years, as applications continue their retreat from the local system and into Web frameworks built on Apache, IIS, Python, PHP, Perl, Ruby, and countless other languages and tools. Against this backdrop, today's official introduction of Firefox 3 may in fact be a watershed event in the history of computing.

The Bottom Line Mozilla Firefox 3.0 Mozilla, mozilla.com/en-US/firefox/ Excellent  9.3 criteria score weight Ease-of-use 10 25% Performance 8 25% Features 10 20% Security 9 20% Value 10 10% Cost: Free download Platforms: Windows 2000, XP, 2003, Vista; Mac OS X 10.4 or later; Linux Bottom Line: Firefox 3 sets new standards for the Web browser. From security and usability through performance, every aspect of Firefox has seen improvements and immediately useful feature additions. Expect Firefox's market share to not only continue to grow, but grow even faster from this point on. About our Reviews and Scoring Methodology

It's no secret that Firefox isn't the most popular browser. Internet Explorer, for better or for worse, enjoys a significant advantage in market share, but data gathered from all corners of the Internet show this advantage eroding. Judging by the traffic at a Web site that handles more than 100,000 unique visitors a day, Firefox gained almost 8 percent over Internet Explorer for the month of May, year over year, moving from just over 26 percent of all visitors to 33 percent. Internet Explorer lost a total of 9 percent to other browsers in that time frame.

Oddly, the difference seems to have been taken up by Apple's Safari, which gained almost 3 percent. These numbers will differ depending on the site -- for instance, sites focused on technology will have higher numbers for Firefox, since most tech-savvy users prefer Firefox over Internet Explorer -- but the general trend shows that Firefox is making significant inroads all over the globe. Judging by the advances in Firefox 3, this is likely to accelerate.

Turning up the heat
Firefox 3 has been in development for years. While not exactly a start-from-scratch rewrite, it's certainly been overhauled, and those changes are apparent in just about every aspect of the browser. The new look is more streamlined, less clunky, and the active elements such as the newly retooled location bar offer a new way to work with the Web. On the back end, the days of Firefox being a notorious memory hog may be over, or at least reduced, and the security measures in the new release are not only far better than any other browser, they also manage to be less intrusive than you might expect. The ease-of-use additions, such as the ability to save a session on exit, and the wonderfully implemented full-page zoom are instant winners.

I've been using Firefox 3 since the November beta, moving through to the very latest release candidates. While I've hit a number of issues over the months, they've all but disappeared in the past few releases. Over the course of the beta period, I've found it difficult to go back to Firefox 2, and certainly difficult to use Internet Explorer; they're missing key Firefox 3 features that have become instantly indispensable.

Smart security
Browser security is of paramount importance. Particularly on Windows, browsers have served as a vector for an enormous number of realized and unrealized vulnerabilities. From malware and spyware to viruses and outright system exploits, all browsers have had their share of missteps. Generally speaking, user education could significantly reduce these occurrences, but that's easier said than done. Firefox 3 makes a valiant attempt, however, with a bevy of new features tuned to the average user.

Clicking the Favicon in the address bar on Firefox 3 offers a quick view of the current site and a button for more detailed information, such as the SSL certificate data, how often you've visited the site, the use of cookies, and so forth. If you happen to come across a forged page (such as those used in phishing attempts), Firefox will block the page and display a surprisingly attractive warning screen explaining the problem and offering a link to return to your home page. There's also a small link allowing you to continue to the content regardless of the warning.

If you browse to an SSL-protected site with a valid certificate, the address bar notes the verified owner of the certificate in a green highlight, giving immediate feedback on the validity of the site. If the site's SSL certificate isn't valid, Firefox 3 presents a method of either quickly navigating away from the site or an option to pull down the certificate and continue to the site. For those of us who use self-signed certificates, this is an extremely useful feature.