Mozilla has released the fourth Alpha for Gecko 1.9.3 layout engine likely to be used in the future Firefox 3.7. This release is being made available for testing purposes only, and is intended as a preview release for web application developers and the testing community. This release includes improvements to performance, JavaScript, Plug-ins and stability.See Release Notes for more information and download/installation instructions. One item that did stand out in the Release Notes:
Performance
One area where people complained about performance was restart performance when applying an update. It turns out that a lot of what made that experience poor wasn’t startup time, it was browser shutdown time. We’ve made a fix since the last preview release that made a whopping 97% improvement in shutdown time. (That’s not a typo, it’s basically free now.)