How to Install Mozilla Firefox 38.0.6 (Stable) on Ubuntu or Linux Mint via PPA

How to Install Mozilla Firefox 38.0.6 (Stable) on Ubuntu 15.04 vivid Vervet, ubuntu 14.10 Utopic Unicorn, Ubuntu 14.04 Trusty Tahr (LTS) or Linux Mint 17.1 Rebecca, Linux Mint 17 Qiana and other ubuntu derivative system via PPA

The Mozilla Firefox project is a redesign of Mozilla's browser component, written using the XUL user interface language and designed to be cross-platform, supporting Linux, Android, Microsoft Windows and Mac OS X operating systems. It is a fast, small and very easy-to-use web browser/navigator/explorer that offers many advantages over other similar products, such as the ability to block pop-up windows and the feature-rich tabbed browsing experience.

Features at a glance

The application offers a well designed graphical user interface that integrates search (powered by Google, Bing, Yahoo, etc.), and industry leading accessibility with Find As You Type - find links and page text by simply typing. As mentioned before, the Firefox browser features comprehensive pop-up controls, which will keep unwanted advertising off your desktop. A tab browsing mode will let you open several pages in a single window, allowing you to load links in the background without leaving the page you're on.

What’s New:

FIXED 33.0.1: Firefox displays a black screen at start-up with certain graphics drivers
NEW OpenH264 support (sandboxed)
NEW Improved search experience through the location bar
NEW Windows: OMTC enabled by default
NEW Slimmer and faster JavaScript strings
NEW Search suggestions on the Firefox Start (about:home) and new tab (about:newtab) pages
NEW Support for connecting to HTTP proxy over HTTPS
NEW New CSP (Content Security Policy) backend
NEW Improved reliability of the session restoration
NEW Azerbaijani [az] locale added
CHANGED JSD (JavaScript Debugger Service) removed in favor of the Debugger interface
CHANGED Proprietary window.crypto properties/functions removed
HTML5 DOMMatrix interface implemented
HTML5 @counter-style rule from CSS3 Counter Styles specification implemented
DEVELOPER Cubic-bezier curves editor
DEVELOPER Paint flashing for browser content repaints
DEVELOPER Display which elements have listeners attached
DEVELOPER New sidebar which displays a list of shortcuts to every @media rule in the current stylesheet
DEVELOPER Editable @keyframes rules in the Rules section of the Inspector
DEVELOPER CSS transform highlighter in the style-inspector
FIXED Various security fixes

Known Issues

UNRESOLVED Fix incomplete downloads being marked as complete by detecting broken HTTP1.1 transfers (237623) Resolved in v33.0
UNRESOLVED PDF.js: With some images, wrong colors could show up. Affects a very small number of PDF
UNRESOLVED Some certificate errors cannot be overridden (1042889)
UNRESOLVED Windows: On some combination of hardware and drivers, the main window could be black. In this case, update your graphics drivers (1083071)