FIREFOX 21 VS FIREFOX 20
"We compare Firefox 21 to Firefox 20 to find out which is the fastest browser when using benchmarks such as HTML5, Octane, Peacekeeper, Sunspider, V8 with Windows 7 Operating System and AMD FX 4300 CPU."
FIREFOX 21 FEATURES
"Firefox 21 has the following new features the Social API now supports multiple providers. NEW Enhanced three-state UI for Do Not Track (DNT). NEW Firefox will suggest how to improve your application startup time if needed. NEW Preliminary implementation of Firefox Health Report."
"Firefox 21 has the following changes such as Ability to restore removed thumbnails on New Tab Page. CSS -moz-user-select:none selection changed to improve compatibility with -webkit-user-select:none. Graphics related performance improvements. Removed E4X support from Spidermonkey."
FIREFOX 21 VS FIREFOX 20 REVIEW