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WebKit is an open source web rendering engine that is integrated into lots of desktop and mobile browsers. Apple's Safari and Mobile Safari, Google's Android browser and Chrome browser (plus the upcoming Chrome OS) and Palm's WebOS all use the WebKit rendering engine.
The BlackBerry has always excelled at e-mail but its web browsing experience leaves much to be desired. Although the browser on the newest phones - like the Storm and the Tour - are much improved, they still aren't as fast and don't render web pages as accurately as the iPhone, Android-based phones, or the Palm Pre.