Firefox 19.0 has been released.   New in Firefox 19 is a built-in PDF reader (no need to rely on Adobe Reader, or other plugins) and improvements to the startup performance.   Firefox 19.0 also includes 8 Security fixes, 4 of which are rated critical.   Firefox (referred to as Fx) is an open source browser developed by Mozilla. The second most popular browser worldwide, Firefox features a customizable user interface that allows you to enhance it using custom themes and Personas. Personas c