As promised, Mozilla Tuesday launched Firefox 3.0, a major update to the open-source browser that adds a new search tool, anti-hacking protection and revamped bookmarking.

The first major revision of Firefox since late 2006, Firefox 3.0 was posted to Mozilla's servers at 1 p.m. EDT, and was so popular it momentarily crashed the US and EU Mozilla download sites.

As it has done before, Mozilla tried to ward off downloaders who had jumped the gun earlier Tuesday by grabbing the final code from the company's public FTP servers. "Downloading them directly can harm our ability to distribute Firefox efficiently," said Mike Beltzner, Mozilla's product lead, in a brief message posted to the company's developer center. Those public FTP servers were inaccessible throughout the morning, apparently overloaded.

Mozilla is promoting Firefox 3.0's availability with an attempt to set a downloading world's record, complete with a page where users have pledged to retrieve the browser Tuesday.

Firefox 3.0 first entered public testing with Alpha 1 in December 2006, with the first of several beta versions released in November 2007. The browser moved to release candidate stage last month. The third, and final, release candidate hit Mozilla's servers less than a week ago.

At one point, Mozilla had set a goal of late 2007 as the launch time for Firefox 3.0.

The updated browser features a redesigned address bar -- dubbed the "Awesome Bar" by some -- that can be used to search for previously-visited pages using keywords or characters in either the URL or the page title; a Google-powered anti-malware blocker that warns users before they reach a site hosting malicious code; and an enhanced bookmark and browsing history tool.

The browser's performance has also been improved and its memory footprint -- Firefox was long drubbed for memory leaks -- has been reduced.

"Firefox 3.0 is evolutionary, not revolutionary," said Ray Valdes, a Gartner research director who tracks browsers. "It's definitely improved, but it doesn't seal the deal. It's not a game changer."

What would have made it such, added Valdes, was if Firefox 3.0 had addressed enterprise concerns, including manageability and deployment issues. The strength of Microsoft's Internet Explorer (IE) in businesses, Valdes said, means that Firefox won't be unseat IE as the world's most popular browser.

According to the most recent data from Net Applications Inc., Firefox accounted for 18.4 percent of all browsers used in May, slotting it in second behind IE (73.8 percent) and ahead of Apple's Safari (6.3 percent).

"Firefox has gotten the low-hanging fruit," said Valdes, who predicted that Mozilla's browser would have a harder time picking up more market share than it had reaching its current second spot.

Firefox 3.0 can be downloaded from Mozilla's site, or the special Tuesday-only record-setting site.