Firefox 18 has been pushed to the beta channel, a week after Firefox 17 became a stable release. Aurora users have been enjoying all the new features for almost two months, but Firefox 18 is now bug-free enough to be ready for a beta.
Also new in Firefox 18 is support for Retina Displays. It's only for Mac users for now, but then again they're the only ones who would benefit at this point.
Standard W3C Touch Events are now supported, alongside Mozilla's own MozTouch events which they'll replace.
This should be great for anyone with a touch-screen desktop, i.e. basically anyone who bought a Windows 8-sporting ultrabook in the past month or so.
The CSS3 Flexbox model, the latest version of the draft spec, is supported in Firefox 18, the CSS3 Flexbox is finally getting wide support in most modern browsers, Opera 12.10 added it as well.
Among the minor fixes, there are some performance improvements for tab switching and faster startup time.
In the experimental realm, Firefox 18 continues to improve support for WebRTC, there's now support for getUserMedia and PeerConnections, the two big pillars of WebRTC.
There's also an option to block the loading of unsecured content on HTTPS pages, though it's disabled by default.