Conversion rate optimization (CRO) involves testing website changes to improve conversion rates. Amazon continually improved its site from the late 1990s to today. CRO has evolved from reliable infrastructure and usability testing to automated optimization testing content targeting across channels. Effective CRO includes benchmarking, discovery through data analysis and goals, developing a testing strategy and roadmap, and executing multivariate tests to determine high-performing variants. Case studies show elements like trust signals, calls to action, design, and value propositions can significantly increase conversions when tested and optimized.