Changes in the beta include better image quality as the developers have changed the algorithm used when scaling HTML imagery, and switching between tabs should be somewhat faster thanks to some performance tweaks. Developers will find that CSS3's Flexible Boxes have now been implemented to allow for a simpler, more responsive style of layout of page elements,
window.devicePixelRatio will now give the ratio between physical pixels and device independent pixels on a display and
@supports is now available to conditionally apply code when a feature is (or isn't) supported. There are also improved startup times and support of the W3C touch events is now implemented, in place of the MozTouch events.
Fixes in the beta include the disabling of insecure content loading on HTTPS pages, a bug that has been in the Mozilla bug system since 2000. For now, the feature requires enabling though through
about:config. There is also, according to the notes, better responsiveness for users working through proxies. Issues still present include Firefox crashing if starting with a locked profile, slow scrolling on gmail, issues with Microsoft's System Restore and a problem with reporting with the
Firefox 18 Beta is available from the Firefox Beta channel and is licensed under the Mozilla Public License 2.0.