what is need Master page

Basically master pages enable you to create a consistent layout for the pages in your application. A ASP.Net master page defines the look and feel and standard behavior of your Main Page that you want for all of the pages (or a group of pages) in your application. later You can create individual content pages that contain the content you want to display.After creating Content Page when users request the content pages, they merge with the master page to produce output that combines the layout of the master page with the content from the content page.
you should navigate MSDN-[ASP.NET Master Pages][^] to know more about Master Page and how to use it.

Advantages of Master Pages in ASP.NET
* It allow you to centralize the common functionality of your pages so that you can make updates in just one place.
* It can make it easy to create one set of controls and code and apply the results to a set of pages.
* It give you fine-grained control over the layout of the final page by allowing you to control how the placeholder controls are rendered.
* It provide an object model that allows you to customize the master page from individual content pages.
Reference Link :- Why do I need ASP.NET Master Pages ?[^]

Hi Vijay,

First you have to take book of ASP.net or web tutorial. get some idea about the ASP.net Server pages.
then Start do some thing, then if you got any problem come here.

go through the below link
http://www.w3schools.com/aspnet/default.asp[^]

Best of luck

refer to this link first

http://www.asp.net/master-pages/tutorials[^]

Master Page mainly Used when u need some static information in all pages, its hard to type code for each and every page.Say if you need to develop 10 aspx page with same header and footer information in this situation you can have a master page where you can have the header and footer information and in all the aspx pages you can refer this master page.

Master page is used for reusability of code.
traditionally developers use copy and paste method to reuse code.But in master page,you do not need to copy paste code.
Master Page in ASP.Net

master page is used to provide a consistent layout to website or to do some work
which is necessary in most of the pages.
to know more :see msdn