Editor’s note: Today, Mozilla released a preview of the Gecko 1.9.3 platform for developers and testers. Check out the Mozilla Developer News announcement reposted below.

A Mozilla Developer Preview of improvements in the Gecko layout engine is now available for download. This is a pre-release version of the Gecko 1.9.3 platform, which forms the core of rich Internet applications such as Firefox. Please note that this release is intended for developers and testers only. As always, we appreciate any feedback you may have and encourage users to help us by filing bugs.

This developer preview introduces several new features, including:

• Support for CSS Transitions. This support is not quite complete: support for animation of transforms and gradients has not yet been implemented.
• Support for SMIL Animation in SVG. Support for animating some SVG attributes is still under development and the animateMotion element isn’t supported yet.
• Support for WebGL, which is disabled by default but can be enabled by changing a preference. See this blog post and this blog post for more details.
• Support for the getClientRects and getBoundingClientRect methods on Range objects. See bug 396392 for details.
• Support for the setCapture and releaseCapture methods on DOM elements. See bug 503943 for details.
• Support for the HTML5 History.pushState() and History.replaceState() methods and the popstate event. See bug 500328 for details.
• Support for the -moz-image-rect() value for <a href="https://developer.mozilla.org/en/CSS/background-image">background-image</a>. See bug 113577 for more details.

and several other significant changes, including:

• On Mac OS X, we render text using Core Text rather than ATSUI.
• We rewrote major parts of the code for handling scrolling. See bug 526394 for details.
• We rewrote the way a snapshot of a document is taken in order to print or print preview. See bug 487667 for details.
• We made significant changes to table border handling. See bug 452319 and bug 43178 for details.
• We made various architectural changes to improve Web page performance.

More information on these changes is in the release notes, as well as the Upcoming Firefox features for developers article on the Mozilla Developer Center.

Please use the following links when downloading this Mozilla Developer Preview:

• Installer for Windows
• DMG for Mac OS X (10.5 or better required)
• Archive for Linux