Chrome jumped from 3.9 percent to 4.6 percent of usage, according to statistics that analytics firm Net Applications publishes based on the 160 million monthly visitors to the network of Web sites using its services. Safari increased from 4.4 percent to 4.5 percent.

Chrome passes Safari for third place in browser usage in December. (Credit: Net Applications)

Chrome's jump came as Google released the first beta version of its browser for Mac OS X and Linux computers. Previously only a developer-preview version was available.

As of last month, Google had been scheduled to graduate the Chrome 4.0 beta version to "stable" on January 12, but mention of that release date has now been removed from the Chromium development calendar. One possible hitch: the Mac beta version and the present Mac developer-preview version don't yet support one key feature of the newer 4.0 incarnation of Chrome: extensions. That means the feature, which lets people customize what the browser can do to some extent, has yet to receive widespread testing on Mac OS X machines.

Also according to Net Applications' statistics, Microsoft's Internet Explorer continued its steady slide, dropping from 63.6 percent to 62.7 percent usage. Most of IE's share loss has been picked up by No. 2 Firefox, but that open-source browser slipped from 24.7 percent to 24.6 percent from November to December.

Better news for Microsoft, and for Web developers who loathe supporting the IE 6 browser first released in 2001: IE 8 has almost edged the older browser aside as the top browser version in use.

IE 8 rose in usage from 19.3 percent to 20.9 percent from November to December, while IE 6 dropped from 22.1 percent to 21 percent.

After crushing Netscape in the first browser wars of the 1990s, Microsoft grew complacent. But the arrival of Firefox and growing usage of other browsers has re-energized the Internet Explorer team.