- The forward button is now hidden until you navigate back.
- Most add-ons are now compatible with new versions of Firefox by default.
- Anti-Aliasing for WebGL is now implemented.
- CSS3 3D-Transforms are now supported.
- New <bdi> element for bi-directional text isolation, along with supporting CSS properties.
- Full Screen APIs allow you to build a web application that runs full screen.
- We've added IndexedDB APIs to more closely match the specification.
- Inspect tool with content highlighting, includes new CSS Style Inspector.
- Fixed bugs.

- Added Type Inference, significantly improving JavaScript performance.
- Added support for querying Do Not Track status via JavaScript.
- Added support for font-stretch.
- Improved support for text-overflow.
- Improved standards support for HTML5, MathML, and CSS.
- Fixed several stability issues.
- Fixed several security issues.

- Added Type Inference, significantly improving JavaScript performance.
- Added support for querying Do Not Track status via JavaScript.
- Added support for font-stretch.
- Improved support for text-overflow.
- Improved standards support for HTML5, MathML, and CSS.
- Fixed several stability issues.
- Fixed several security issues.

- Fixed Bugs.

- Add-ons installed by third-party programs are now disabled by default.
- Added a one-time add-on selection dialog to manage previously installed add-ons.
- Added Twitter to the search bar.
- Added a preference to load tabs on demand, improving start-up time when windows are restored.
- Improved performance and memory handling when using <audio> and <video> elements.
- Added Cross-Origin Resource Sharing (CORS) support for cross-domain textures in WebGL.
- Added support for HTML5 context menus.
- Added support for insertAdjacentHTML.
- Improved CSS hyphen support for many languages.
- Improved WebSocket support.
- Fixed several stability issues.

- Fixed Bugs.

- Drastically improved memory handling for certain use cases.
- Added a new rendering backend to speed up Canvas operations on Windows systems.
- Bookmark and password changes now sync almost instantly when using Firefox Sync.
- The 'http://' URL prefix is now hidden by default.
- Added support for text-overflow: ellipsis.
- Added support for the Web Timing specification.
- Enhanced support for MathML.
- The WebSocket protocol has been updated from version 7 to version 8.
- Added an opt-in system for users to send performance data back to Mozilla to improve future versions of Firefox.
- Fixed several stability issues.
- Fixed several security issues.

- Fixed Bugs.

- Fixed Bugs.

- The address bar now highlights the domain of the website you're visiting.
- Streamlined the look of the site identity block.
- Added support for the latest draft version of WebSockets with a prefixed API.
- Added support for EventSource / server-sent events.
- Added support for window.matchMedia.
- Added Scratchpad, an interactive JavaScript prototyping environment.
- Added a new Web Developer menu item and moved development-related items into it.
- Improved usability of the Web Console.
- Improved the discoverability of Firefox Sync.
- Reduced browser startup time when using Panorama.
- Fixed several stability issues.
- Fixed several security issues.

- Fixed Bugs.

- Added support for CSS animations.
- The Do-Not-Track header preference has been moved to increase discoverability.
- Tuned HTTP idle connection logic for increased performance.
- Improved canvas, JavaScript, memory, and networking performance.
- Improved standards support for HTML5, XHR, MathML, SMIL, and canvas.
- Improved spell checking for some locales.
- WebGL content can no longer load cross-domain textures.
- Background tabs have setTimeout and setInterval clamped to 1000ms to improve performance.
- Fixed several stability issues.
- Fixed several security issues.

- Fixed several security issues.
- Fixed several stability issues.

- Firefox 4 is based on the Gecko 2.0 Web platform.
- JavaScript execution speeds up to six times faster than the previous version.
- New capabilities for Web Developers and Add-on Developers such as hardware accelerated graphics and HTML5 technologies.
- Completely revised user interface.

- Fixed Bugs.

- Fixed several security issues.
- Fixed several stability issues.

- Fixed several security issues.
- Fixed several stability issues.

- Fixes a critical security issue that could potentially allow remote code execution.

- Fixed several security issues.
- Fixed several stability issues.

- Fixed a single stability issue affecting a limited number of users.

- Introduced support for the X-FRAME-OPTIONS  HTTP response header. Site owners can use this to mitigate clickjacking attacks by ensuring that their content is not embedded into other sites.
- Fixed several security issues.
- Fixed several stability issues.

- Fixed a single stability issue affecting some pages containing plugins.

- Fixed several security issues.
- Fixed several stability issues.

- Firefox 3.6.6 modifies the crash protection feature to increase the amount of time that plugins are allowed to be non-responsive before being terminated.

- Firefox 3.6.4 provides uninterrupted browsing when there is a crash in the Adobe Flash, Apple Quicktime or Microsoft Silverlight plugins.
- Fixed several security issues.
- Fixed several stability issues.

- Firefox 3.6.3 fixes a critical security issue that could potentially allow remote code execution.