The success of any website greatly depends upon the returning customers. Those customers have enjoyed your service. They have a experience of your website before, enjoyed their stay and felt satisfied with the services you offered to them. The trust of the customers on websites increases as they keep on coming back to the site. When he starts believing you completely, he recommends your website to their friends, relatives, family members etc. Then those people start visiting your site and as it is recommended by someone who they know, they trust on you and purchases products from you. Thus, this converts those visitors to customers and thus, increases you sales.