Google on Friday released a revved-up version of Chrome as rivals Microsoft and Mozilla beefed up their own champions for the competitive Internet browsing software arena.

In keeping with the arrival of the lunar year of the rabbit, Google product managers Jeff Chang and Li Chan touted the latest test version of Chrome as "quick as a bunny."

The latest Chrome release came a week after Microsoft fielded an Internet Explorer 9 (IE9) "release candidate" boasting improvements in speed, security, privacy, and website graphics capabilities.

IE9 had been downloaded more than two million times as of Friday, according to Ryan Gavin, the senior director of the IE team.

"We are especially excited to see the number of partners and developers embracing IE9 and taking advantage of the performance capabilities," Gavin said in a blog post.

Mozilla last week released a test version of its Firefox 4 web browser with enhancements that included a "Do Not Track" feature people could use to signal websites that they don't want their online activities recorded.

"We've continued our work to improve performance and stability, while also implementing a 'Do Not Track' privacy feature to provide more control over online behavioral tracking," Mozilla said.

Firefox debuted in 2004 as an innovative, communally crafted open-source browser released as an option to Internet Explorer.

Google last month released extension software for its Chrome browser that lets users opt out of being tracked by a growing set of companies adopting industry privacy standards regarding online advertising.

"Keep My Opt-Outs" lets people opt out of having snippets of code referred to as "cookies" installed on their computers to track online behavior for the purpose of targeting ads.

Microsoft "Tracking Protection" was built into IE9, but users need to be savvy enough to activate the feature and create lists of the third-party websites that they do not want to track their behavior.

Internet Explorer is the most widely used Web browser in the United States followed by Firefox, Chrome and Apple's Safari.