Google's policy is to support only the current version of a browser, and its immediate predecessor.

Giving up on IE8, however, is markedly different than dumping IE7.

Last year, when Google said it would stop supporting IE7, that edition accounted for just 7% of all browsers used worldwide, according to Web analytics firm Net Applications.

IE8, on the other hand, was the most widely-used browser edition in the world last month, with a usage share of 25%. Of those who ran one version or another of IE, nearly half, or 47%, ran IE8 in August.

Windows XP faces its own end-of-life cutoff; Microsoft will serve users with that operating system's final security update in April 2014. But like IE8, Windows XP remains a major presence. Last month, Net Applications measured XP's global usage share at 42.5%, just behind the three-year-old Windows 7's 42.8%.