The recent release of upgrades to the world's three most popular Web browsers, Windows Internet Explorer, Mozilla Firefox, and Google Chrome, makes it a good time to consider whether to explore a change.

Windows Internet Explorer (IE), the oldest of the three, was updated to version 9 on March 14 (and changed its name from Microsoft Internet Explorer in the process).

If you're still using Windows XP, IE 9 is not for you, since Microsoft discontinued support for it. Unlike other browsers, IE 9 only runs on Windows PCs, unless you use extra software from third parties targeted to Web designers using other operating systems to let them see how their sites look to IE users.

IE 9 is a good choice if you're a Microsoft fan and are running Windows 7 or Windows Vista. Its interface, resembling that of Google Chrome, is less cluttered and easier to use than previous versions of IE. Another trick learned from other browsers is the ability to run Web searches directly from the address bar. IE 9 is also faster than previous versions.

Since Microsoft began bundling IE with Windows in 1995, preventing people from having to undertake a separate download procedure, IE has been the most popular browser, reaching a peak of 95 percent of users in 2002, according to Search Engine Journal (www.searchenginejournal.com). It has steadily decreased in popularity since then, though it's still the most popular browser, accounting for 45 percent of the market today, according to StatCounter (http://statcounter.com/).

Mozilla Firefox is the spiritual descendant of the first popular graphical Web browser, NCSA Mosaic, released for free to the public in 1993 by the National Center for Supercomputing Applications and leading to the explosion of the Web's popularity. Firefox is a product of the non-profit Mozilla Foundation (www.mozilla.org), with version 1.0 introduced in 2004.

Firefox 4 was released on March 22, and it was downloaded in record numbers, 7.1 million downloads in the first 24 hours, according to Mozilla, double that of IE 9 during its first 24 hours. Firefox 4 runs on Windows 7, Vista, XP, and 2000; Mac OS X 10.4 and later; Linux; and other platforms. Firefox currently accounts for 30 percent of the browser market, according to StatCounter.

As with IE, the latest Firefox is a big improvement over its predecessor, and as with IE, the interface is cleaner and easier to use. It also features improved security, and it's faster. According to testing by a number of magazines and Web sites, however, Firefox is the slowest of the three major browsers, though typical users won't notice much difference in real-world use.

Firefox's most important distinction is the number of "add-ons" that third-party software developers have written for it. This continues under version 4, though as is typical with upgrades not all add-on developers have upgraded their add-ons in time for the release of the new version.

Google Chrome is the newest kid on the block, with the company most known for its search service having introduced the first version in 2008. Chrome 10, released on March 8, builds upon Chrome's innovations, now copied by other browsers, in making its interface uncluttered, with the focus on the Web page you're at, and in making Web search as easy as typing in a Web address.

Chrome 10 improves the product's security features, helping you avoid being tricked into downloading malicious files. It's the fastest of the three major browsers. It works slightly better than other browsers with Google Docs, the word processor, spreadsheet, presentation, and similar programs offered for free by Google through your Web browser.

Chrome continues to gain in popularity. The biggest change over the last year in the browser market, according to StatCounter, has been the rise of Chrome's market share from 7 to 17 percent (IE fell from 53 to 45 percent, and Firefox fell slightly as a result of Chrome from 31 to 30 percent). Chrome 10 is available for Windows 7, Vista, and XP; Mac OS X 10.5 and later; and Linux.

The most popular browser for Apple Macintosh computers is Safari, which since 2003 has come bundled with them. A recent survey by About.com (www.macs.about.com) found that 28 percent of Mac users preferred Safari, though it was closely followed by Firefox-cousin Camino (22 percent), Firefox (21 percent), and Chrome (19 percent).

All of the above Web browsers are free, supported by, among other means, Web search companies that pay for their product to be the browser's default search tool.