Content Security Policy
From Just Solve the File Format Problem
A Content Security Policy, defined in a W3C candidate recommendation, lets sites set security restrictions on access of objects within a page, to prevent risky cross-site activity. This has come under some criticism for its ability to block things users may want, such as bookmarklets.
Policies are linked via an HTTP header Content-Security-Policy (or its equivalent meta tag). They consist of a series of semicolon-separated directives.
