Here's a list of the changes in this release:
What’s New:
NEW: Windows: Firefox is now easier to update with one less prompt (User Account Control) NEW: Page Source now has line numbers CHANGED: Line breaks are now supported in the title attribute CHANGED: Improvements to "Find in Page" to center search result CHANGED: URLs pasted into the download manager window are now automatically downloaded DEVELOPER: The column-fill CSS property has been implemented DEVELOPER: Support for the text-align-last CSS property has been added DEVELOPER: Experimental support for ECMAScript 6 Map and Set objects has been implemented FIXED: OS X: WebGL performance may be degraded on some hardware (713305)