Safari 4 is rocking the internet world as just in three days it has scored 11 million downloads out of which 6 millions are windows users. One of the most touted new features is the browser’s advanced bytecode Nitro JavaScript engine that executes JavaScript up to six times faster than Microsoft’s Internet Explorer 8 and up to four times faster than Firefox 3.1, according to the SunSpider JavaScript Performance test.
HTML 5 Technology
Safari 4 includes HTML 5 support for offline technologies and support for advanced CSS effects.  Apps and data can be stored in a traditional SQL-like database serving as an app cache or as a “super cookie,” which stores data in a cookie format.

Features
Full History Search allows users to search through titles, Web addresses and the complete text of recently viewed pages. Cover Flow flips through Web history or bookmarks. Safari 4 also offers Smart Address Fields to automatically complete Web addresses from a list of suggestions, Search Fields to fine-tune searches with recommendations from Google Suggest or a list of recent searches, and Full Page Zoom for a closer look at any Web site without degrading the quality of the site’s layout and text.
Using what it calls “speculative loading,” Safari loads ahead of time documents, scripts and style information needed to view a Web page, so pages are ready when a user wants to view them. The new JavaScript Debugger tool cycles through a page’s JavaScript and stops when it finds exceptions or erroneous syntax. Users also can pause JavaScript, set break points and evaluate local variables.