Just having a website is not enough, you need to make sure it is optimized for success. Websites are there to help your business being more traffic, sales, leads, brand awareness, raise customer service levels & feedback/reviews. There are various factors which help you achieve those goals. This infographic will help you understand this in more depth. Do you know that $1.9 trillion of retail sales in 2013 were web influenced.
Other things like responsive design and how website optimization can help you increase effectiveness of your campaigns by over 78%.