NEWHOUSE NEWS SERVICE - If your Mac is running OS X, you no doubt already know that Apple's operating system is immune to the Internet ailments that plague Windows, such as spyware, Web-page hijacking and, of course, Windows viruses. And you've probably had a chance to dump Microsoft's tired OS X browser, Internet Explorer, in favor of one the best Web browsers ever designed, Apple's superb Safari. But Safari has company. Firefox, the Web browser favored by millions of Windows users, is available in a version for OS X, as a free download from http://www.mozilla.org.I'm a big Safari fan, but...