You probably have a Facebook app with a tab set up. As the owner or administrator of the page, you can add any tabs that you want, and even make them the default tab for visitors who are not yet fans or administrators of your page.
So how to do it:
- Build the Facebook app and make sure you create a version with a maximum width of 520 pixels.
- In your application’s settings, configure the tab options to indicate the narrow version of your application.
- Go to the application profile page and with links on the side select "Add to my page.", Select the page to which you want to add the application.
- In your page’s settings, set the default tab to the “Application” tab that you just added.
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