Apple has released a public beta version of Safari 4 - its web browser for Mac and Windows PCs.

Safari 4 is built on the Nitro JavaScript engine which, according to Apple, runs JavaScript 4.2 times faster than Safari 3, up to 30 times faster than IE 7 and three times faster than Firefox 3.

The browser also features HTML 5 offline support, allowing users to access documents created in web-based applications even when they're not online and can handle advanced CSS Effects to ensure users can see the clearest and sharpest graphics possible.

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"Safari 4 is the fastest and most efficient browser for Mac and Windows, with great integration of HTML 5 and CSS 3 web standards that enables the next generation of interactive web applications," said Philip Schiller, Apple's senior vice president of worldwide product marketing.

Apple also claims Safari 4 is the first browser to pass the Web Standards Project's Acid3 test, which examines how well a browser handles web standards including JavaScript and XML.

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Built using Apple's WebKit, which also formed the basis of Google's web browser Chrome, Safari 4 for Windows also features a new-look which Apple claims "fits the look and feel of other Windows XP and Windows Vista applications".

Safari 4 also offers a number of new functions. Top Sites displays a tiled preview of frequently visited web pages, allowing users to easily jump between pages, while Full History Search lets users browse through, titles, URLs and the full text of recently viewed pages, making it easy to return to sites they've visited before.

The Smart Address Field offers suggestions for website addresses based on browsing history and bookmarked web addresses and the Smart Search Field suggests search terms based on previous Google searches.

The Tabs on Top feature allows users to drag and drop tabs in the web browser to re-order them, while the new Full Page Zoom function ensures the quality of text and images on a website isn't reduced when a user zooms in.

Apple has also integrated iTunes Cover Flow scrolling library into the browser, to offer an unusual view when searching through browsing history or bookmarks.

Safari 4 is available to download now from Apple's website. Both Mac and Windows versions are available.

See also: Apple Safari 4 beta is a Beautiful browser