Perform A/B testing without user feedback

Website visitor needs to avoid dismissing checkout process on e-commerce website.
1 answer

Perform A/B testing using Javascript

On checkout page include small Javascript script which is going to send to server which button is clicked.
Create two versions of checkout page (both with different colors of ,,Cancel" button)

Serve each version to 50% of visitors (every second visitor gets one version).

Count how many times user clicked on each button. Version that has less clicks on ,,Cancel" button gives better solution for design of Cancel button.