NoScript

Allow active content to run only from sites you trust, and protect yourself against XSS attacks.

Updated September 17, 2008

Additional Information:
Winner of the “2006 PC World World Class Award”, this tool provides extra protection to your Firefox.
It allows JavaScript, Java and other executable content to run only from trusted domains of your choice, e.g. your home-banking web site, and guards the “trust boundaries” against cross-site scripting attacks (XSS).
Such a preemptive approach prevents exploitation of security vulnerabilities (known and even unknown!) with no loss of functionality…
Experts do agree: Firefox is really safer with NoScript ;-)