http://adsafe.org/

http://www.jslint.com/

"JavaScript, the programming language of the web browser, is not a secure language. Any script in a page has intimate access to all of the information and relationships of the page. This makes use of mashups and scripted advertising unacceptably risky. ADsafe makes it safe to put guest code (such as third party scripted advertising or widgets) on a web page. ADsafe defines a subset of JavaScript that is powerful enough to allow guest code to perform valuable interactions, while at the same time preventing malicious or accidental damage or intrusion."