Firefox 3 alpha 4 has been released by Mozilla . The new alpha version is better known as Gran Paradiso and includes a number of updates , mostly aimed at developers. The main feature is improved support for offline application.

Firefox 3 alpha 4 includes a user extension library for javascripts. The Gecko 1.9 layout engine has also been improved.

New alpha versions will be released on a monthly basis, Mozilla said. Its new schedule shows that alpha versions 5 and 6 will be released at the end of May and June respectively. The complete beta version will be released on 31 July.

Firefox 3 is the next upgrade for Mozilla's popular open-source browser and due for release in the last quarter of this year. It will feature a whole new bookmarking system, new ID management tools and support for offline web applications.

Firefox 3 alpha 4 is available to download here .