Opera 9, which had been in beta since April, includes features designed to improve the efficiency of Web surfing, enhance security and allow users greater control over the content they view.
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A security bar has also been added to Opera 9, a response to the prevalence of phishing scams and identity theft. The security bar aims to reduce users' encounters with phishing scams and also includes technology to strengthen blocking of pop-up advertisements.
Opera 9 also offers a thumbnail feature, which enables users to mouse over an open tab to see a thumbnail preview of the page
Opera 9, which is offered as a free download, runs on a variety of platforms, from Windows to Mac to Linux. It also supports BitTorrent's file distribution technology.
"For Opera 9, we worked hard to push the limits of what people expect from a Web browser," Jon von Tetzchner, Opera Software chief executive, said in a statement.