Unfortunately, many viewers abandon a Web site after a short visit. Why does this happen? And what can we do about it?
As Kissmetrics notes:
“Attracting a potential customer is hard enough. Grabbing their interest and retaining them is even more difficult. It’s important to design your site so that user frustration is kept to a minimum, thereby maximizing customer retention. Below are some examples of what not to do when designing your Web site.”

Source: What Makes Someone Leave A Website?