Mozilla Firefox's newest browser, Firefox 4 has gotten off to a roaring start with 7 million downloads in 24 hours, topping its main browser rival, Internet Explorer 9.

Mozilla released the fourth major version of its popular Firefox browser on Tuesday morning; and by Wednesday it had reached the 7 million downloads mark. In contrast, Microsoft's latest Internet Explorer browser, IE9 had only 2.5 million downloads in its first 24 hours.

That said, IE9 is limited to computers running the Windows Vista and Windows 7 operating systems, which have less than 30 percent of the market compared to Windows XP's nearly 70 percent share, according to netmarketshare.com.

The latest version of Firefox is the fastest yet, claims Mozilla. It is available on Windows, Mac OS X and Linux in more than 80 languages.

With dramatic speed and performance advancements across the board, Firefox is between two and six times faster than previous releases. Major enhancements to the JavaScript engine make everything from startup time to page load speed to graphics and JavaScript performance screaming fast in Firefox, the company wrote on a blog announcing its release.

Along with the speed and JavaScript performance, Mozilla says the latest Firefox's look is completely redesigned. It has easier navigation and contains security features like Do Not Track and Content Security Policy, which prevent cross-scripting attacks.  It also supports HTML5 and has hundreds of add-ons and extensions.

According to research company StatCounter, Firefox has made significant share gains over the past few years in terms of competing with Microsoft Internet Explorer. While IE is still the champion with 45 percent share, Firefox's second place 30 percent share is up four percent from 2008. IE is down 15 percent, having to compete with not only Firefox, but Google Chrome, Apple Safari and mobile browsers as well.