In case you haven’t been keeping up with the Firefox nightly builds/beta, here is a list of features that have been added to the RC version of Firefox 5:
- Added support for CSS animations;
- The Do-Not-Track header preference has been moved to increase discoverability;
- Improved canvas, JavaScript, memory, and networking performance;
- Improved standards support for HTML5, XHR, MathML, SMIL and canvas;
- Improved spell-checking for some locales;
- Improved desktop environment integration for Linux users;
- WebGL content can no longer load cross-domain textures;
- Background tabs have setTimeout and setInterval clamped to 1000ms to improve performance; and
- The Firefox development channel switcher introduced in previous Firefox Beta updates has been removed.
New Source: http://www.ubergizmo.com/2011/06/mozilla-firefox-5-almost-out-the-door/