Your conversion rate is probably the most important metric for your online business. Better conversions means more sales, as simple as that.
Good web design is one of the major reasons why your website may or may not convert. Over at the Entrepreneur I found a very helpful article about web design and conversion which I think you should take a look at.
It contains all the pointers that can help you design a website that will convert your visitors to customers. Check the article out, it is very helpful.