New features of Firefox 15 include silent background updates, support for SPDY version 3 (a Google-backed protocol intended to reduce page load times), and enhancements to WebGL support.
HTML5 support continues to improve, with native support for the Opus audio codec, support for the 'played' attribute of <audiop> and <video> elements, and support for the 'media' attribute of the <source> element.
Given that one of the popular features of Firefox is the large number of add-ons, users are likely to benefit from the way version 15 optimises memory usage by add-ons.
Additional new features can be found in the mobile (Android) version of Firefox 15.
They include a native UI for tablets (which also delivers faster startup), search improvements, import of bookmarks and history from the standard Android browser, and implementation of the find in page feature.
Bug fixes for the mobile version cover areas including text selection in web content, copy and paste, and forms.
Firefox 15 also delivers 16 security fixes, seven of them regarded as critical.
That's the greatest number of security fixes in one version since Firefox switched to the rapid release model.