E-commerce web usability is a game of probability, not possibility. If you try to allocate the same weight to elements that attract product-oriented purchasers as you do comparison shoppers and casual browsers, your site will fail all of them.
You need to review which groups of users you have the most of, then allocate your site's real estate to serve their needs. Web analytics is your friend here. Once you spot the patterns and know what kind of primary and secondary visitor groups you have, it's time to roll up your sleeves and get to work prioritizing changes to your website.
Tim Ash is the author of the bestselling book Landing Page Optimization, and CEO of SiteTuners. A computer scientist and cognitive scientist by education (his PhD studies were in Neural Networks and Artificial Intelligence), Tim has developed an expertise in user-centered design, persuasion and understanding online behavior, and landing page testing. In the mid-1990s he became one of the early pioneers in the discipline of website conversion rate optimization. Over the past 15 years, Tim has helped a number of major US and international brands to develop successful web-based initiatives. Companies like Google, Expedia, Kodak, eHarmony, Facebook, American Express, Canon, Nestle, Symantec, Intuit, AutoDesk and many others have benefitted from Tim's deep understanding and innovative perspective.
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