Earlier you were introduced to a feature called Master Pages, but what exactly are they? The idea behind them is the one that's been around since the early days of development. The idea that you can inherit the layout of one page for use in another is the one that has kept many developers scrambling with Includes and User Controls. This is where Master Pages come into play. They allow you to lay out a page once and use it over and over. By doing this, you can save yourself countless hours of time, as well as being able to maintain the look and feel of your site from a single place. By implementing a Master Page and using ContentPlaceHolders, your page is able to keep its continuity throughout.
In Chapter 4, you saw a simple implementation of a Master Page that contained two ContentPlaceHolder controls (ContentPlaceholder1 and Head, identified by their IDs). The Default.aspx
page was set up to use the Master Page that was created. We'll expand upon all of this in a bit more detail...