Firefox 19 is slated for an official release on Tuesday, it will be released in few hours. If you can’t wait to grab the download you can do so through the Mozilla FTP servers. Downloads are available for Windows, Mac and Linux. Browse the FTP folder and identify your platform file and download.
Firefox 19 is released as a beta version on Jan 10th 2013, it includes improvements, bug fixes and features compared to the previous version of the popular browser. Most notable is the built-in PDF viewer to allow users to view PDF files natively in the browser itself. Along with the desktop beta, beta version of the mobile browser also released which included theme support and other improvements.
Release notes for Firefox 19 are not yet posted but you can see the beta release notes to have an idea of what you can expect from the latest build. If you want to wait for the official release keep a watch on the official Firefox download page.
Update: Released now download here.