Although it's not intended for public consumption, a new build of Firefox 3 Alpha 5 (code name Gran Paradiso) is available for download from Mozilla. In this release, add-ons created for Firefox 2 may not work. For end users, Firefox 2 remains the latest public version. The final public release for Firefox 3 is not expected until the fall of 2007. See a slide show of Firefox 3 Alpha 5 here.
Intended for developers and beta testers, Firefox 3 Alpha 5 features a new rendering engine. The Gekko 1.9 rendering engine will introduce some changes. For example, Firefox 3 will no longer support Windows 95, 98, and Me, and for the Mac OS X, versions 10.2 and earlier will not longer be supported. There will also be numerous changes made to the Document Object Model (DOM) in Gekko 1.9, which will affect developers more than end users. Also, there will be changes in the way Firefox renders frames within its display and the way object tags are handled, as well as changes in event threading.
What's truly exciting about this alpha release is a feature called Places. As first seen in Firefox 2 Alpha 1, then temporarily tabled, Places returns in Firefox 3 Alpha 5--kind of. The functionality exists in this release for a new side panel that allows you to control your bookmarks, RSS subscriptions, and browser history in one convenient space. Places uses the open-source SQLite database, giving it greater extensibility and the ability to back up and restore bookmarks; however, this also means it's incompatible with earlier Firefox bookmarks.
Also new in this build are Web-based content handlers, greater search engine keyword support, a new password manager, something called Extension Manager (EM), the beginnings of an intentity network, better integration with Mac OS X look and feel, some offline applications support, and site specific preferences.
Also, there's help for cross-site scripting, when the browser makes a request for a page not found on the target server. This is a favorite technique for criminal hackers. Mozilla proposes that Firefox receive a response if the server explicitly allows other sites to access pages, otherwise the browser will throw away the response and throw an exception.