jQuery is a cross-platform JavaScript library designed to simplify the client-side scripting of HTML. It is free, open-source software using the permissive MIT License. Web analysis indicates that it is the most widely deployed JavaScript library by a large margin.
Visual Website Optimizer is an easy to use A/B testing tool that allows marketing professionals to create different versions of their websites and landing pages using a point-and-click editor (no HTML knowledge needed!) and then see which version produces maximum conversion rate or sales.