X-FRAME-OPTIONS

Back in January of 2009, I announced IE8’s support for a new header-specified directive: X-Frame-Options , that can be used to mitigate ClickJacking attacks.

Combating ClickJacking With X-Frame-Options - EricLaw's IEInternals

http://blogs.msdn.com/b/ieinternals/archive/2010/03/30/combating-clickjacking-with-x-frame-options.aspx

Adoption of X-FRAME-OPTIONS Header

http://blogs.sans.org/appsecstreetfighter/2009/10/15/adoption-of-x-frame-options-header/ Late 2008, Jeremiah Grossman and Robert Hansen publicized the clickjacking problem and got the web app security experts all trying to come up with solutions.
http://blogs.msdn.com/b/ie/archive/2009/01/27/ie8-security-part-vii-clickjacking-defenses.aspx As we planned Internet Explorer 8, our security teams analyzed the common attacks in the wild and the trends that suggest where attackers will be focusing their attention next.

IEBlog : IE8 Security Part VII: ClickJacking Defenses