1. Create a new MasterPage
Right click your project, go to “Add” and then “New Item…” and select MasterPage. Name it something useful, like “main.master” and hit ok. You should be presented with a barebones XHTML skeleton. Notice that your skeleton has this tag in it:
2. Link your old pages to your MasterPage in the Page Directive
In your <%@ Page directive, add the following attribute: MasterPageFile="~/YourMasterPage.Master"
3. Tell the MasterPage What Content Goes Where
If you only have one ContentPlaceHolder, you will add the following tag around all of your content in your .aspx pages:
And that’s it! That’s really all there is to it! Just apply steps 2 and 3 to each of your .aspx pages. There is an optional step for those who may have changed their pages’ codebehind inheritance: