Yahoo Inc. on Thursday launched a beta release of a toolbar for Mozilla Firefox, a sign of the increasing popularity of the open-source web browser.

The Sunnyvale, Calif., portal giant is providing Firefox users with a version of the toolbar Yahoo currently provides for Microsoft Corp.'s Internet Explorer. The purpose of the software, which is installed under the browser's address bar, is to give people one-click access to Yahoo services.

Features in the toolbar beta include search that looks for information on the web, Yahoo or on a particular website. There's also a search history to check previous searches.

Translation of web pages written in foreign languages is available through the use of Babel Fish, a translation tool provided by Overture Services Inc. that ships with the Yahoo Toolbar.

In addition, the beta software provides mail notification and alerts for subscribers of Yahoo's email service.

Mitchell Baker, president of the Mozilla Foundation, which oversees the development of Firefox, said in a joint statement with Yahoo that the announcement "demonstrates the popularity of the browser and the success of the Mozilla platform."

Indeed, the most recent figures from WebSideStory Inc., a San Diego-based web analytics firm, indicate that Firefox has about 5 percent of the browser market, while Internet Explorer has about 90 percent. The Mozilla Foundation says the browser has been downloaded 23 million times since the 1.0 version was released in November.

The Firefox toolbar does not support Yahoo's Anti-Spyware feature, which the company plans to include in a future update. The toolbar is available only for Windows, with versions for the Mac OS X and Linux expected soon.