Clickjacking is a malicious technique of tricking Web users into revealing confidential information or taking control of their computer while clicking on seemingly innocuous Web pages. (Source: http://en.wikipedia.org/wiki/Clickjacking)

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Here is a simple example where clicking anywhere on the screen (except header and footer) takes the user to another website. http://www.collegehumor.com/video:1928558

Prevention

Currently it seems like there is only one way of protecting against such attacks and that is by using the ‘NoScript‘ add-on for Firefox.