Although it’s a little bit of a hassle to be busy continuously whitelisting sites that you want to allow, but the ability to block scripts is probably one of the most effective PC security measures available.
NoScript 5.0, a popular script blocker (and more) for Firefox has just been released to the public after two release candidate build releases. The browser add-on is a script blocker first and foremost. It blocks any script from running on sites you visit, unless you whitelist them. The approach makes it one of the best add-ons from a security point of view, but means that you will have to adjust website permissions regularly as sites may fail to load completely or partially due to scripts not being loaded when the site is opened in the Firefox web browser.