Mozilla Firefox is a free, open-source and cross-platform web browser for Windows, Linux, MacOS X and many other operating systems. It is small, fast and easy to use, and offers many advantages over other web browsers, such as tabbed browsing and the ability to block pop-up windows. Firefox also offers excellent bookmark and history management, and it can be extended by developers using industry standards such as XML, CSS, JavaScript, C++, etc. Many extensions are available. Note: Mozilla ceased supporting Firefox 1.5.0.x in May 2007. All users are strongly encouraged to upgrade to Firefox 2 (see www/firefox).