Actully All HTML controls are state-less ie;-these can not 
store any type of clients inputs.when ever we send the page 
to server it will send this page as fresh one.so we loose 
the data what we have entered.

To store all these data (temporarly) in clients browsers ,
.Net provide a concept that is known as View state .View 
state store the data in encoding format,so that one can not 
gues it easily.