Mozilla officially launched Firefox 19 for Windows, Mac, Linux, and Android with lower CPU limits to support 15m more phones

Changes & Improvements:- 

• The improvements include a built-in PDF viewer on the desktop and theme support on Google’s mobile platform. All users of old Firefox versions can upgrade it automatically.  
• The biggest addition in this release is PDF.js, a JavaScript library intended to convert PDF files into HTML5. PDF.js loads and renders PDFs quickly directly in the browser, and because it uses standard HTML5 APIs, it can run on many platforms (PCs, tablets, and phones). 
• Firefox for Android is now available to phones with minimum requirements of 600MHz, 512MB, HVGA, including the LG Optimus One, T-Mobile myTouch 3G slide, HTC Wildfire S, and ZTE R750. 
• Debugger now supports pausing on exceptions and hiding non-enumerable properties. 
• There is now a Browser Debugger available for add-on and browser developers (experimental, set devtools.chrome.enabled to true).