Hi, ASP.NET master pages allow you to create a consistent layout for the pages in your application. A single master page defines the look and feel and standard behavior that you want for all of the pages (or a group of pages) in your application. You can then create individual content pages that contain the content you want to display. 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. Regards, Iftikar

master page is a page where we create common design for our web pages.

Refer to this link for details: Master page : Gives us a way to create common set of UI elements that are required on multiple page s of our website. means you create one page design use it for all page. Content Page : The ASP.NET web page that will use master page to have the common UI elements displayed on itself. it will use the master page to get the design. http://www.codeproject.com/Articles/333650/Beginner-s-Tutorial-on-Master-Pages-in-ASP-NET