How to deny loading a page into a frame of a third-party site

A modern method to deny loading pages of your site into frame (FRAME or IFRAME HTML-element) on another site is using of X-Frame-Options HTTP-server response header.

Available values for X-Frame-Options:

Loading page into frame is denied.
Loading page into frame is permitted only in case of frame is located on a page of same site that loading page belongs to.
The page can only be displayed in a frame on the specified origin.

DENY and SAMEORIGIN values are supported by all modern browsers including IE8+.

ALLOW-FROM uri value is supported by Firefox 18+.