Added in MSIE8 and Mozilla Firefox 3.6.9, Apple Safari 4, IE8, and Google Chrome 2 are several mechanisms to defend against cross-domain forgeries.
Supported Values:
X-FRAME-OPTIONS: DENY
X-FRAME-OPTIONS: SAMEORIGIN
You can explicitly set this value for ApacheHTTP in the httpd.conf file, your .htaccess files or code it into the page(s) by the application itself.