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Most people don't give a second thought to their web browser, the program you're using to read this page. There was a time around the turn of the century when you were just as likely to be using a browser by Netscape as one by Microsoft. Now, though, there's a good chance it's the latter.

Unless you've heard of Firefox.

Since its introduction in 2004, Mozilla Firefox has eaten away at the market share of Microsoft's Internet Explorer.

For much of the first half of this decade, up to 95 per cent of web traffic, by some estimates, was going through IE. Microsoft's browser had essentially won the first round of the browser wars of the late 1990s over Netscape Navigator.

Now, that number is closer to 85 per cent.

Most, but not all, of those users have switched to Firefox. In 2003, Microsoft announced that it would stop development of IE for Mac, so many Apple users now use Safari, the browser that comes with every Mac, or Firefox. A smaller proportion of people use other browsers, including Opera.

So why did so many web surfers switch over to Firefox in 2004?

Some say it's the customization that's possible with Firefox. Extensions are enhancements that can be installed to add new functions to the Firefox browser. These extensions can do anything from blocking ads to adding a constantly updated weather report.

I count myself among the people who can't live without my favourite extensions, but not everyone uses a web browser as much as, say, I do, or can be bothered to endlessly add extensions and tweak settings to get their browser's behaviour exactly right.

But even without any customizations, Firefox offered two things that IE 6 couldn't at the time: tabbed browsing and a pop-up blocker.

Users were getting frustrated with the clutter and interruptions generated by pop-up ads under IE 6 and Firefox offered immediate relief. (Windows XP Service Pack 2, released in August 2004, included a pop-up blocker, but many XP users didn't install the update or didn't know about the feature.)

Tabbed browsing allows Firefox users to have multiple web pages open at once inside the same browser window, instead of opening a new window for every separate page.

Internet Explorer 6, which was released in August 2001, had grown stale, with no new features added for three years. Firefox came along to satisfy the appetite for something new, and arose Microsoft from its slumber.

In February 2005, Bill Gates announced that Microsoft was working on Internet Explorer 7, and it released a beta version that summer and a public preview in January 2006.

The most striking feature of IE 7 is the browser's new minimalist design. Where once there were a dozen or so buttons in the top-left corner, there are now only two: forward and back. The buttons for stop, reload, home and the rest have been moved elsewhere on the toolbar. The result is a much cleaner interface, but the buttons can't be moved back to their familiar spots if that's the way you prefer it.

IE 7 includes many features familiar to Firefox users, including a pop-up blocker, support for RSS feeds, a customizable search box and tabbed browsing.

Microsoft actually takes the tab concept a step further than Firefox with Quick Tabs, a button that displays a preview of all the tabs currently open in the browser. It's similar to Exposé, a feature on newer versions of the Mac OS that displays a preview of all open programs. IE 7's Quick Tabs can be replicated in Firefox with an extension called foXpose.

Speaking of which, IE 7 doesn't support extensions the way Firefox's does, and extension addicts won't be impressed with the level of customization IE 7 offers. It does have something called add-ons, but there's some confusion about what an add-on actually is.

Bringing up IE 7's add-on manager lists the browser plug-ins installed, familiar names such as Flash for animation or QuickTime for video. What's new is that the manager also allows you enable and disable these add-ons and it's also possible to start IE in "No Add-ons" mode.

But Microsoft's web page for IE add-ons also includes third-party programs that change the browser's behaviour, such as the ad blocker WebWasher and a variety of download managers. These programs don't appear in IE 7's add-on manager and aren't disabled when the browser is started in "No Add-ons" mode.

IE 7 will come with every new computer that runs Microsoft's next operating system, Windows Vista — expected sometime in 2007 — and will also be available for Windows XP, provided you've upgraded your system with the latest service packs.

The company isn't planning to make versions of IE 7 to run on Windows 98, Windows 2000, Mac OS or any other operating system. That means Firefox and other browsers will run on millions of computers that IE 7 simply won't.

Still, for people who buy new PCs after Vista comes out, IE 7 will offer the two things — the pop-up blocker and tabbed browsing — that caused some people to leave IE 6 for lacking. For them, there won't be that immediately visible advantage for switching to Firefox.

Yes, IE 7 has adopted many of the features that Firefox has had for more than two years. And yes, Firefox is more flexible and can be customized to an amazing degree. But for many users, IE 7 will be more than good enough.