Often with ecommerce sites success is not a matter of how good you are but rather how good you look.
Consumers often judge how professional and how trustworthy an online store is by nothing more than its aesthetics. While many online retailers are experts in their field (i.e., apparel, tools, and toys), they are not necessarily experts in graphic design or website development. They know all about the products they sell, but they may not know much about, say, white space, alpha transparency, or PHP.