Ars Technica has a nice look at Firefox 3.0 now that alphas and nightly builds are rolling out.
The reflow 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.

We probably won’t be seeing the new JavaScript VM until Gecko 2.0 / Mozilla 2.0 which is inline for Firefox 4.0, but who knows. Maybe this timeline changes with the Adobe donation?

