In Web site development with
ASP.NET, the
Master Page can contain a ContentPlaceHolder control that is
used to define a region of the Master Page
rendering that can be substituted with content from a page associated to the
Master Page.
ASP.Net Tutorials: Creating a Layout Using Master Pages Just as Themes and Skins allow you to factor out style definitions from your page code and maintain them in a common file, Master Pages do the same for page layout.
Customizing and Managing Your Site's Appearance When a page that uses a master page (i.e., a content page) is requested, ASP.NET merges the content page and master page together (assuming of course that both have already been compiled).
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