Tomorrow is Download Day, says Firefox 3 maker Mozilla, and the company will attempt to set a world record for software downloads when it unleashes its latest Web browser. Firefox 3 brings better performance, security, and an improved design and is, according to my own tests, the best Web browser available on any computing platform.

Firefox 3 includes a visual refresh with a more prominent navigational control, improved extensibility features, an intelligent new location bar and bookmarks and history organizational structure that makes it easier to find saved and previously-visited Web sites, built-in protection against malicious Web sites trying to deliver malware, and a number of other updates.

To promote the new release, Mozilla is sponsoring a Download Day tomorrow, June 17, during which it hopes to set the Guinness Record for software downloads in a single day. More information about this promotion can be found at the Spread Firefox Web site.

Firefox rose to relative prominence from humble beginnings: After Netscape spun off Mozilla a decade ago, the organization began working on an open source version of Netscape's complex browser suite, which included email, newsgroup, chat, and Web page editing in addition to Web browsing capabilities. Worried that the product had become too unwieldy, a core set of developers began working on a lightweight Web browser using Mozilla's rendering engine in 2002. That product, originally named Phoenix, became Firebird briefly, and then was finally renamed to Firefox.

When it debuted in late 2004, Firefox faced an uphill battle: Microsoft's Internet Explorer controlled over 95 percent of the market for Web browsers. Today, however, IE controls less than 73 percent worldwide, with Firefox seizing over 18 percent. In many countries, however, Firefox's market share is even higher, and it's been growing steadily. Its success has been great enough to cause Mozilla to incorporate itself and to cause Web site developers to ensure that their content is equally accessible to Firefox users as it is to those still using IE.

Past successes aside, Firefox faces new challenges as the Internet-using public moves increasingly to mobile devices. Mozilla still doesn't have a mobile version of its flagship browser available, and of course Apple's Safari has also seen sharp growth thanks to the iPhone, which includes a version of that browser. Mozilla is, of course, working on a mobile version of Firefox, and looking ahead to this next battleground.

My review of Firefox 3 is now available on the SuperSite for Windows.