The Firefox project (formerly Firebird, which was formerly Phoenix) is a redesign of Mozilla's browser component, written using the XUL user interface language and designed to be cross-platform.
Firefox is a small, fast and very easy to use browser that offers many advantages over other web browsers, such as the ability to block pop-up windows and the tabbed browsing.

· Comprehensive popup controls to keep unwanted advertising off your desktop;
· A tab browsing mode that lets you open several pages in a single window, allowing you to load links in the background without leaving the page you're on;
· Integrated search (powered by Google);
· Industry leading accessibility with Find As You Type - find links and page text by simply typing;
· Simplified privacy controls that let you cover your tracks more effectively;
· A streamlined browser window that lets you see more of the page than any other browser while at the same time being more configurable;
· A large variety of free downloadable extensions and themes that add specific functionality and visual changes to the browser.

Requirements:
· Pentium 233 MHz (Recommended: Pentium 500MHz or greater)
· 64 MB RAM (Recommended: 128 MB RAM or greater)
· 52 MB hard drive space

What's New in This Release:
· Blacklisted a few invalid HTTPS certificates
· Updated localizations for 29 locales
· Added Vietnamese localization, bringing the total languages available in Firefox 4 to 83
· Support for the proposed Do Not Track ("DNT") header
· Connection status messages are now shown in a small overlay
· WebGL is enabled on all platforms, but, like for other hardware acceleration features, many buggy drivers or driver versions are blocked
· The default homepage design has been refreshed
· Firefox no longer switches into offline mode automatically
· Overhaul of the bookmarks and history code, enabling faster bookmarking and startup performance
· Per-compartment garbage collection is now enabled, reducing work done during complex animations
· The Firefox Sync setup experience has been greatly improved across desktop and mobile devices
· Additional polish for the Firefox Add-ons Manager
· Uses JägerMonkey, a new, faster JavaScript engine
· Certain rendering operations are now hardware-accelerated using Direct3D...