火狐浏览器是一个速度快、占用内存小、设计美观的开放源代码 web 浏览器。在 2004 年，其公开发行后，火狐浏览器是第一个挑战了微软 Internet Explorer 主导地位的浏览器。自那时以来，火狐浏览器一贯成为在全球范围内最受欢迎浏览器排名前 3。火狐浏览器之所以取得了如此的欢迎度是因为其主要特色：简单、有效的用户界面、超快的网页浏览速度和强大的安全功能。浏览器在开发人员中极为流行，因其开发使用开放源码，加上有很多高级用户的活跃论坛。
Mozilla 的很多资源投入到创建一个简单但有效的用户界面方面，其旨在使浏览速度更快，操作更容易。他们开发的标签浏览（选项卡）功能已被其他大多数浏览器采用。最近几年，Mozilla 也着重于最大化浏览区，通过简化工具栏上的控件，最终简化到一个火狐浏览器按钮 （其中包含的设置和选项），然后是后退/前进两个按钮。URL 框功能直接使用谷歌搜索，以及称为智慧型网址列（Awesome Bar）的自动预测/历史记录功能。在 URL 框中右侧有书签、历史记录和刷新按钮。URL 框中的右侧是一个搜索框，在这里您可以自定义搜索引擎选项。在视图按钮外，展示您在 URL 下面看到的内容。在其旁边，您能看到下载历史记录和主页按钮。
个性化 & 开发
狐浏览器用户界面最好的一个功能是自定义。只需右键单击导航工具栏就可以自定义单个组件，或者您可以拖动您想要移动的项目到您需要的位置。火狐浏览器内置的加载项管理器允许您寻找并安装加载项，内置到浏览器内，您还可以查看评级、建议和说明。成千上万的可自定义主题允许您自定义浏览器的外观和感觉。站点作者和开发人员可以使用 Mozilla 的开源平台和增强 API 创建高级内容和应用程序。
What's New in Firefox 3
Firefox 3 is based on the new Gecko 1.9 Web rendering platform, which has been under development for the past 27 months and includes nearly 2 million lines of code changes, fixing more than 11,000 issues. Gecko 1.9 includes some major re-architecting for performance, stability, correctness, and code simplification and sustainability. Firefox 3 has been built on top of this new platform resulting in a more secure, easier to use, more personal product with a lot 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. Identity verification is prominently displayed and easier to understand. In later versions, Extended Validation SSL certificate information will be displayed.
* Malware Protection: malware protection warns users when they arrive at sites which are known to install viruses, spyware, trojans or other malware. You can test it here (note: our blacklist of malware sites is not yet activated).
* New Web Forgery Protection page: the content of pages suspected as web forgeries is no longer shown. You can test it here.
* 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 do not provide secure updates will be disabled.
* Anti-virus integration: Firefox will inform anti-virus software when downloading email and executables.
* Vista Parental Controls: Firefox now respects the Vista system wide parental control setting for disabling file downloads.
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.
* 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.
* 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 Vista: Firefox's menus now display using Vista's native theme.
* Integration with the Mac: Firefox now uses the OS X spellchecker and supports Growl for notifications of completed downloads and available updates.
* 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.
* Location bar & auto-complete: type the title or tag of a page in the location bar to quickly find the site you were looking for in your history; favicons, bookmark, and tag indicators help you see where results are coming from.
* Smart Places Folder: quickly access your recently bookmarked and tagged pages, as well as you more frequently visited pages with the new smart places folder on your bookmark toolbar.
* Bookmarks and History Organizer: advanced search of your history and bookmarks with multiple views and smart folders to store your frequent searches.
* 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).
* 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.
* Native Web page forms: HTML forms on Web pages now have a native look and feel on Mac OS X and Linux (Gnome) desktops.
* 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.
* 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.
* Speed: Major architectural changes (such as the move to Cairo and a rewrite to how reflowing a page layout works) put foundations in place for major performance tuning which have resulted in speed increases.
* Memory usage: Over 300 individual memory leaks have been plugged, and a new XPCOM cycle collector completely eliminates many more. Developers are continuing to work on optimizing memory use (by releasing cached objects more quickly) and reducing fragmentation.