At first, Blake Ross says Mozilla's Firefox isn't really in a battle with Microsoft's Internet Explorer, even though a major new version of each browser is coming out this month. The Firefox co-creator is half right: Firefox spreads by word of mouth, not IT dictate, and it's backed by a nonprofit instead of the world's largest software company. Time to play nice?

On second thought, the 21-year-old Ross lets the fighting words fly. "Firefox brought Microsoft back to the table, but they make no guarantees how long they'll stick around," he says. "I can't imagine why any individual--let alone an IT department--would bet on a company with a proven track record of gross abandonment."

Time to go another few rounds. Five long years after the release of Internet Explorer 6--which provided the final knockout punch to one-time champ Netscape--Microsoft is about to release a major upgrade to IE. New features such as tabbed browsing and integrated search mimic those already in Firefox, causing some observers, Ross among them, to describe IE7 as a "catch-up" release. Mozilla's not standing still --Firefox 2.0 will be released within days of IE7.

For Microsoft, IE7 represents a key piece of software in its critically important "Live" initiative to deliver Windows, Office, and other products as services over the Web. "The browser is the gateway to the Web, and therefore the window to Live services," says IE7 product manager Gary Schare.

Browsers should matter to businesses because they're the interfaces through which employees and customers will spend ever more of their screen time. Internet Explorer, Schare says, is "probably the most commonly used piece of Windows." Web sites and intranet portals are merely the low-hanging fruit when it comes to how browsers are used. Wikis, blogs, RSS feeds, search engines, and many more Web productivity tools are increasingly accessed and viewed through browsers, and a growing variety of mobile devices let you take a browser with you.

Internet Explorer has many advantages in its quest to remain the dominant browser, but Microsoft will have to save IE7 from the vendor's own bad habits. Previous versions were slack on security, standards compliance, and new features. Bill Gates admitted as much in March. "In a sense, we're doing a mea culpa and saying we waited too long to do a new browser release," Microsoft's chairman said.

IE7 promises a lot. For users, the biggest addition is tabbed browsing, which lets multiple Web pages appear in one browser window. It's one of Firefox's most popular features and could become even more powerful coupled with business applications. "A lot of our apps are moving to the Web, and having to click different tabs rather than opening different windows is simply easier," says Kevin Moll, desktop management team leader for the 892-lawyer firm Foley & Lardner. Another time-saver is a search bar integrated into the browser--here, too, Firefox led the way.

But it's security that's been Internet Explorer's No. 1 shortcoming, according to IT pros and Microsoft itself. "Nothing pains you more than people bailing on your product because they don't trust it," Schare says. Among IE7's security advances: a parsing module identifies and discards dangerous URLs, turns off most ActiveX controls by default, and offers color-coded warnings in the URL bar based on whether sites are trusted. Another is a built-in phishing filter that spots malicious pages before they reach the user.

Microsoft will distribute IE7 as an automatic update, but many companies won't let it be pushed to employees just yet. A reputation for buggy new releases precedes Microsoft. "We have no desire to be on the bleeding edge of browser technology," says Dave Pluke, VP of IT at engineering firm Ericksen Roed. "Stability and security are paramount." Pluke says his company's IE7 upgrade is more than a year off. Foley & Lardner plans to wait until next year, when IE7 will be part of the firm's Windows Vista upgrade. IE7 is the default browser in Vista; Microsoft last week confirmed that Vista is on track to be available for businesses in November.