The open source Mozilla Foundation has issued Release Candidate 1 of a major upgrade to its Firefox browser.
Firefox version 1.5 is a big jump from current version 1.0.7, and offers improved pop-up blocking, better navigation to users and enhanced support for web standards.
Firefox 1.5 Release Candidate 1 has been released to enable testers to spot any last-minute glitches before the final version is distributed to internet users later this year.
Another preview of the code is expected before the commercial release.
Version 1.5 will also be supported by an improved software updating system to deal with security updates and product enhancements, and will come with improved integration with the Apple Mac operating system.
Firefox has been downloaded more than 100 million times since being launched in November 2004, and has about 8% of the browser market. Microsoft's Internet Explorer has about 85% of the market.