Framekiller

A framekiller (or framebuster or framebreaker) is a piece of JavaScript code that prevents a Web page from being displayed within a frame. A frame is a subdivision of a Web browser window and can act like a smaller window. This kind of script is often used to prevent a frame from an external Web site being loaded from within a frameset without permission, often as part of clickjacking attack.

Read more about Framekiller:  First Framekillers, Modern Framekiller, Framekiller Killers, Framekiller Limitations