This is a reference to a post on MSDN. It discusses frame-busting technique to defend websites against click-jacking.
Web developers can send a HTTP response header named X-FRAME-OPTIONS with HTML pages to restrict how the page may be framed. If the X-FRAME-OPTIONS value contains the token DENY, IE8 will prevent the page from rendering if it will be contained within a frame. If the value contains the token SAMEORIGIN, IE will block rendering only if the origin of the top level-browsing-context is different than the origin of the content containing the X-FRAME-OPTIONS directive. For instance, if http://shop.example.com/confirm.asp contains a DENY directive, that page will not render in a subframe, no matter where the parent frame is located. In contrast, if the X-FRAME-OPTIONS directive contains the SAMEORIGIN token, the page may be framed by any page from the exact http://shop.example.com origin.
When rendering is blocked by the X-FRAME-OPTIONS policy, a local error page is presented that explains the restriction and provides a link which opens the frame in a new window. When displayed in a new window rather than a sub-frame, content is no longer subject to ClickJacking.