Mobile application

First you have to decide which type of application you want to develop. because building mobile applications is very broad and different than web applications.

Thanks Kumar. Give any Ref. site

Mobile Application can Browser based applications (WAP) or Native application which are platform dependent. So if you want to develop mobile applications in .net you can go for
Windows Phone applications which are developed in silverlight. But If you want to develop browser based applications you can do it normal asp.net and or you can use JQuery Mobile framework with asp.net and directly run on browser.