I am new in MVC 3. What is the reason to use two web.config files?

Wha
View has its own config. If you are dealing with areas Then you will come to know about more than one config.
Actually The point is that view's Web.Config is for view specifc configutation such as blocking direct access to the views.
EDIT 1: More Explaination as asked in comments.
The web.config file exists in the Views folders to prevent access to your views by any means other than your controller. In the MVC design pattern, controllers are supposed to route requests and return a rendered view to the calling client. That means localhost9999://Home/Index.cshtml should not be directly accessible.