JavaScript is a scripting or programming language that allows you to implement complex features on web pages — every time a web page does more than just sit there and display static information for you to look at — displaying timely content updates, interactive maps, animated 2D/3D graphics, scrolling video jukeboxes, etc. — you can bet that JavaScript is probably involved. It is the third layer of the layer cake of standard web technologies, two of which (HTML and CSS) we have covered in much more detail in other parts of the Learning Area.

For example, you want to see if shifting a “Buy now” button to the sidebar of a page instead of keeping it on the top will improve its click-through rate. The current design is called the “control” version (version A). Version B is called the “challenger.” Then you can start testing these two versions by showing them to a predefined number of site visitors to see which version is clicked more. It’s good to divide your sample groups equally and randomly.

Usually, A/B testing is used to test landing pages, welcome emails, and ads. It is better to focus on things that are most likely to have a big impact: search modals, call-to-action buttons, headlines, images, product descriptions, navigation, social sharing buttons etc.

The terms ‘A/B testing’ and ‘split testing’ are often used in the same meaning. But in fact, they are two different types of tests – A/B testing compares two versions by changing one element and split testing compares two distinct designs.