Firefox 3 is based on the Gecko 1.9 Web rendering platform, which has been under development for the past 34 months. This new platform includes more than 15,000 changes to improve performance, stability, rendering correctness, and code simplification and sustainability. Firefox 3 is built on top of this new platform resulting in a more secure, easier to use, more personal product with a lot more under the hood to offer website and Firefox add-on developers.
One-click site info: Click the site favicon in the location bar to see who owns the site and to check if your connection is protected from eavesdropping. Identity verification is prominently displayed and easier to understand. When a site uses Extended Validation (EV) SSL certificates, the site favicon button will turn green and show the name of the company you're connected to.
Malware Protection: malware protection warns users when they arrive at sites which are known to install viruses, spyware, trojans or other malware.
New Web Forgery Protection page: the content of pages suspected as web forgeries is no longer shown.
New SSL error pages: clearer and stricter error pages are used when Firefox encounters an invalid SSL certificate.
Add-ons and Plugin version check: Firefox now automatically checks add-on and plugin versions and will disable older, insecure versions.
Secure add-on updates: to improve add-on update security, add-ons that provide updates in an insecure manner will be disabled.
Anti-virus integration: Firefox will inform anti-virus software when downloading executables.
Vista Parental Controls: Firefox now respects the Vista system-wide parental control setting for disabling file downloads.
Effective top-level domain (eTLD) service better restricts cookies and other restricted content to a single domain.
Better protection against cross-site JSON data leaks.
Easier to Use
Easier password management: an information bar replaces the old password dialog so you can now save passwords after a successful login.
Simplified add-on installation: the add-ons whitelist has been removed making it possible to install extensions from third-party sites in fewer clicks.
New Download Manager: the revised download manager makes it much easier to locate downloaded files, and you can see and search on the name of the website where a file came from. Your active downloads and time remaining are always shown in the status bar as your files download.
Resumable downloading: users can now resume downloads after restarting the browser or resetting your network connection.
Full page zoom: from the View menu and via keyboard shortcuts, the new zooming feature lets you zoom in and out of entire pages, scaling the layout, text and images, or optionally only the text size. Your settings will be remembered whenever you return to the site.
Podcasts and Videocasts can be associated with your media playback tools.
Tab scrolling and quickmenu: tabs are easier to locate with the new tab scrolling and tab quickmenu.
Save what you were doing: Firefox will prompt users to save tabs on exit.
Optimized Open in Tabs behavior: opening a folder of bookmarks in tabs now appends the new tabs rather than overwriting.
Location and Search bar size can now be customized with a simple resizer item.
Text selection improvements: multiple text selections can be made with Ctrl/Cmd; double-click drag selects in "word-by-word" mode; triple-clicking selects a paragraph.
Find toolbar: the Find toolbar now opens with the current selection.
Plugin management: users can disable individual plugins in the Add-on Manager.
Integration with Windows: Firefox now has improved Windows icons, and uses native user interface widgets in the browser and in web forms.
Integration with the Mac: the new Firefox theme makes toolbars, icons, and other user interface elements look like a native OS X application. Firefox also uses OS X widgets and supports Growl for notifications of completed downloads and available updates. A combined back and forward control make it even easier to move between web pages.
Integration with Linux: Firefox's default icons, buttons, and menu styles now use the native GTK theme.
Star button: quickly add bookmarks from the location bar with a single click; a second click lets you file and tag them.
Tags: associate keywords with your bookmarks to sort them by topic.
Smart Location Bar: type in all or part of the title, tag or address of a page to see a list of matches from your history and bookmarks; a new display makes it easier to scan through the matching results and find that page you're looking for. Results are returned according to their a combination of frequency, and recency of visits to that page, ensuring that you're seeing the most relevant matches. An adaptive learning algorithm further tunes the results to your patterns!
Library: view, organize and search through your bookmarks, tags and browsing history using the new Library window. Create or restore full backups of this data whenever with a few clicks.
Smart Bookmark Folders: quickly access your most visited bookmarks from the toolbar, or recently bookmarked and tagged pages from the bookmark menu. Create your own Smart Bookmark Folders by saving a search query in the Library.
Web-based protocol handlers: web applications, such as your favorite webmail provider, can now be used instead of desktop applications for handling mailto: links from other sites. Similar support is available for other protocols (Web applications will have to first enable this by registering as handlers with Firefox).
Download & Install Add-ons: the Add-ons Manager (Tools > Add-ons) can now be used to download and install a Firefox customization from the thousands of Add-ons available from our community add-ons website. When you first open the Add-ons Manager, a list of recommended Add-ons is shown.
Easy to use Download Actions: a new Applications preferences pane provides a better UI for configuring handlers for various file types and protocol schemes.
Improved Platform for Developers
New graphics and font handling: new graphics and text rendering architectures in Gecko 1.9 provides rendering improvements in CSS, SVG as well as improved display of fonts with ligatures and complex scripts.
Color management: (set gfx.color_management.enabled on in about:config and restart the browser to enable.) Firefox can now adjust images with embedded color profiles.
Offline support: enables web applications to provide offline functionality (website authors must add support for offline browsing to their site for this feature to be available to users).
A more complete overview of Firefox 3 for developers is available for website and add-on developers.
Memory usage: Several new technologies work together to reduce the amount of memory used by Firefox 3 over a web browsing session. Memory cycles are broken and collected by an automated cycle collector, a new memory allocator reduces fragmentation, hundreds of leaks have been fixed, and caching strategies have been tuned.
Reliability: A user's bookmarks, history, cookies, and preferences are now stored in a transactionally secure database format which will prevent data loss even if their system crashes.