Place all the contents inside the "Content Place holder" of a inherited Master file.
it may be anything, images, text...etc.
eg:
<% @ Page Language="C#" MasterPageFile="~/Master.master" Title="Content Page 1" %>
<asp:Content ID="Content1" ContentPlaceHolderID="Main" Runat="Server">
Main content, images, text...etc
</asp:Content>