According to Mozilla’s official counter page, Firefox 4 has been downloaded more than seven million times so far. Impressive, but its first-day numbers were still short of the Firefox 3 release in June 2008, which actually earned a Guinness World Record for tallying eight million downloads in 24 hours. By comparison, Microsoft said its Internet Explorer 9, released last week, was downloaded 2.35 million times in its first 24 hours.

Update: Mozilla has now compiled its official 24-hour download count:

Within 24 hours of Firefox 4 being announced it had been downloaded 7.1 million times, this is in addition to the more than 3 million people who were already running the release candidate that became our final version

Note: screenshot is from a little more than 24 hours after official release.

Firefox faces ever-increasing competition in the browser market, though browser users do seem to be creatures of longtime habit. Internet Explorer was still the leading global browser as of February 2011, with 45.4 percent market share, according to StatCounter. It was followed by Firefox with 30.4 percent and Google Chrome with 16.5 percent.

This latest version of the browser offers a number of new features. Among them: Private browsing, location-aware surfing, support for emerging HTML 5 standards such as plug-in-free video and audio playing, and better JavaScript performance. It’s that last improvement that’s most noteworthy since Mozilla claims that Firefox 3.5 is twice as fast as Firefox 3, and an astonishing 10 times faster than Firefox 2.0.

Nice features, all of them, and ones that certainly reflect the goal of Firefox’s creators at the Mozilla Foundation: To upgrade the Web. “What we’re actually trying to do,” Mozilla Chairman Mitchell Baker said at our D7 conference in May (see video highlights below), “…is improve the Web itself….Our main goal is to make more capabilities available, and right now, the browser is the main delivery mechanism….We’re trying to be the delivery mechanism upon which others build innovations.”

And upon which Firefox builds market share. Though it is currently the world’s second-leading browser, with a 22.5 percent share of the global Web browser market, Firefox faces some formidable competition these days from Microsoft (MSFT), Apple (AAPL) and now Mozilla partner Google (GOOG), which is bearing down upon it with its latest “don’t-be-evil” bulldozer, Chrome.