Version 4 Public Beta. Added features include a "Top Sites" tool that tracks the user's most recently viewed pages, and notifies the user of content updates; Cover Flow support for history and bookmarks; and full history search. A new, radically redesigned UI, with the tabs now on top, has been implemented. The new Nitro engine (previously code named SquirrelFish Extreme) renders JavaScript 4.2 times faster than the previous release of Safari according to Apple test reports. A newly redesigned set of Developer Tools, Auto-Detect of Google searches and websites, and full page zooming have also been added.[9] The "save page as standalone web applications" feature from the first developer preview of Safari 4 has been removed. The full feature list on Apple's website describes the other 150 new features of Safari 4.[10]