Mozilla has finally released a beta of Firefox 3.0 after 27 months of development.

The company is keen to stress that Firefox 3 Beta 1 is a developer preview release rather than a finished product, and is making the download available for "testing purposes only".

Firefox 3 Beta 1 integrates the Gecko 1.9 rendering engine, and features improved security aimed at combating phishing attacks, new antivirus software and Windows Vista-style parental control settings.

Mozilla also claims improved integration with Windows Vista and Mac OS, in addition to better zooming and enhanced tab controls. More than two million lines of code have been changed and 11,000 issues fixed.

"These beta releases are targeted at web developers and our testing community to gain feedback before advancing to the next stage in the release process," Mozilla said in statement.

"The final version of Firefox 3 will be released when we qualify the product as fully ready for our users."