If you’re like most people, you’re probably using the web browser that came with your computer. The market share of web browsers today bears that out. Microsoft’s Internet Explorer controls 74.9% of the market, while Apple’s Safari controls 5.7%, according to NetApplications.com of Aliso Viejo, Calif.

Over the years, and continuing to the present, companies have been fighting tooth and nail to get you to use their browsers, with Microsoft being the most aggressive, even to the point of getting into antitrust trouble in the U.S. as well as abroad. Microsoft made it impossible for other browser developers to compete with it when the software behemoth included its own browser with Microsoft Windows and prevented computer companies from including competitive browsers if they wanted to be able to offer Windows on their PCs.

Internet Explorer was able to reach a peak of 96% of the browser market in 2002, but then Microsoft was found guilty of monopolization and in violation of the Sherman Act in United States v. Microsoft Corp. The company escaped being split up, but it was forced to permit greater competition.

The main competition today comes from Firefox (www.mozilla.com/en-US/firefox ), a product of the nonprofit Mozilla Foundation and the spiritual descendent of the original graphical web browser Mosaic, which was introduced in 1993. Despite the fact that it typically has to be downloaded and installed, Firefox currently has 17.3% of the market, according to Net Applications. Firefox runs on various versions of Microsoft Windows as well as Mac OS X and Linux. And like Internet Explorer and Safari, Firefox is free.

With free browsers doing their jobs as well as they do, programs you need to pay for have had a hard row to hoe. The leading commercial browser, Opera (www.opera.com), controls a scant 0.7% of the market, though browsers based on Opera are used on a number of “smartphones” and video game consoles because of its small footprint. Many other niche browsers (some free, some pay) have an even smaller market share among desktop and laptop computer users.

Microsoft isn’t the only aggressive player here. In March, Apple generated criticism and controversy by including the latest version of Safari (www.apple.com/safari), the first nontest version for Windows, as part of its automatic update routine for users of Apple’s popular iTunes digital media player and QuickTime web video and audio player.

Many Windows users, according to anecdotal and media reports, downloaded and installed the browser thinking they needed it to run iTunes or QuickTime. As long as you have the hard disk space (and most people have plenty to spare), no harm will come from having more than one browser installed on your PC. In fact, testing out different browsers can be a fun and useful activity. But Apple, though not trying to thwart competition, was being a bit too tricky with its tactics in trying to gain market share among Windows users.

Companies have been fighting so fiercely to get you to use their free browsers for a number of reasons. In the past, web search companies paid serious money to be a browser’s default search tool, and other companies with a web presence paid to be listed in the default set of bookmarks that came with the browser. In the future, most computing may be done not with desktop programs, such as those included in Microsoft Office, but with programs, with the browser being the gateway and with huge online advertising revenues at stake.

Since the pre-Mosaic days, I’ve tested many browsers. Today, I use Firefox most, appreciating its breadth of features and security. Safari, however, renders pages quickly, has an innovative text search tool that highlights all occurrences on a webpage of the text you’re searching for, and is worth checking out in particular if you use a PC at work and a Mac at home

If you’re the intrepid sort, kicking the tires of the next version of your current browser can be enjoyable as well. Such testing is designed in part to help the program’s developers discover bugs and improve the product before the final release.

Firefox 3 Beta 4 (www.mozilla.com/en-US/firefox/all-beta.html) was released in March and is faster than previous betas, including Firefox 2. The first beta of Internet Explorer 8, Beta 1 (www.microsoft.com/windows/products/winfamily/ie/ie8/default.mspx), was also released in March. Microsoft describes it as a preview for web designers to help them ready their webpages for the future launch of the program.