A large number of browser exploits take advantage of JavaScript and third-party plugins like Java and Flash. NoScript is a popular multi-award winning Firefox add-on that blocks all such scripts and plugins, and allows you to intelligently and selectively execute them only on trusted websites.
I have always felt that using NoScript borders on the verge of paranoia, since it hinders normal web browsing experience. However, a lot of people obviously don’t mind this, since NoScript can protect users against scary click-jacking exploits, XSS vulnerabilities and even zero-day exploits that haven’t been discovered yet. Many Opera and Chrome users have been requesting similar functionality for a long time. However, most NoScript implementations for the aforementioned browsers have been limited due to the rigid nature of their APIs. Fortunately, Eric Wong has found an ingenious way of make NoScript work within the framework of Opera and Chrome’s extension library.
NotScripts is a NoScript inspired extension for Opera and Chrome, that utilizes storage quota allocated to HTML5 applications and UserJS files to offer many of the functionalities present in NoScript. It supports both whitelist (everything is blocked, unless explicitly allowed) and blacklist (everything is allowed, unless explicitly blocked) approaches, and allows you to block scripts either temporarily or permanently.
NotScripts is still not perfect, and as mentioned earlier, taking a whitelist approach might create usability problems. Nevertheless, NotScripts is the best implementation of NoScript I have seen for either browser.