The Mozilla Security Blog has an article A Glimpse Into the Future of Browser Security that the CSF feature is now available in preview builds of Firefox.
Content Security Policy is intentended to mitigate against the web application vulnerabilites XSS and CSRF which increased considerabely over the last few years. Grab a preview build of Firefox from the download page and help testing this new feature. The demo page has currently 11 individual tests if your browser supports CSP (showing PASS) or not (showing FAIL). ■