[laurihy]

The magnitude of the help of course depends on the type of business, but generally the answer is yes.

Usually, when people make decisions without full information, they fall back on simple heuristics. One of the most common one is to derive hidden features of the product or brand from the visible ones. As an example, I don't know if service X is reliable (as I don't have prior experience or other knowledge), but since the price is high, I assume that price and quality (reliability) are connected and the same goes for looks. If the business looks (as in graphic design) nice, then I assume that the business is also nice.

At least in the context of eCommerce, the perceived quality of the information is among the biggest factors affecting the perceived trust and risk. It has been researched, that both trust and risk affect consumers intention (in addition to the potential benefit) and thus when consumer trusts the service and perceives low risk, she's more likely to make a purchase.

This comment is more focused on the web graphics -point of the question and visual parts of the design. I'm aware that design is much more than just deciding the right shade of blue.