ArsTechnica have posted an in-depth look at Mozilla's new project, Firefox 3.0. The significant jump from 2.0, released a mere 2 months ago is mainly due to Mozilla's use of the new Gecko rendering engine.
Mozilla has officially released the first public alpha build of Firefox 3.0. Codenamed Gran Paradiso, Firefox 3 includes the new Gecko 1.9 rendering engine which leverages the open-source Cairo rendering framework and features heavily re factored re flow algorithms that improve Firefox layout functionality and resolve some long-standing CSS bugs.
The re flow improvements in Gecko 1.9 (included in the latest Gran Paradiso nightly build, but not the alpha release) finally enable Firefox to pass the Acid 2 test, a CSS test case developed by the Web Standards Project to illuminate flaws in HTML/CSS rendering engines. To pass the Acid 2 test, browsers must comply with W3C standards and provide support for a wide variety of features that are considered relevant by Web designers. The Acid 2 test has been passed by several other browsers, including Safari, Konqueror, and Opera, but not Internet Explorer. Passing Acid 2 is considered to be a significant milestone in Firefox development.