With Internet Explorer 9, Microsoft showed Wednesday it's trying to retake the browser initiative. IE remains the Net's dominant browser. But perversely, it became something of a technology underdog after Microsoft vanquished Netscape in the browser wars of the 1990s and scaled back its browser effort. That left an opportunity for rivals to blossom--most notably Firefox, which now is used by a quarter of Web surfers, but also Apple's Safari, which now runs on Windows as well as Mac OS X, and G...