Facebook Site URL?

There is a tab called Website. Just put URL int here. Hope it helps

Updated as of 29/05/2012:

It is now called 'Website with Facebook Login'

Updated as of 17/7/2014:

On Settings > Basic
Click on "Add Platorm"
Then select "Website"
Enter URL(s) in the form that appears

You're right. Facebook apps can be daunting at times. This is what the problem is:

The Site URL specifies where the facebook app page redirects to, while the App Domain is used for Authentication (such as login feature, etc).

You are specifying as your App Domain (some-other-domain.com) is a different base URL from your Website >> Site URL (yoursite.com/myfacebookapp).

Use the same for both:

• App Domain:: yoursite.com
• Site Url:: yoursite.com/myfacebookapp

The App Domain is typically located in the top under the
-Your App Settings >> Basic >> Basic Info.

The Website: Site URL is currently located in
-Your App Settings >> Basic >>"How your app integrates with Facebook">> Website >> Site URL.

:: Set the Site URL you want the page to redirect to, then, if you would like authentication services for that page, include root domain of your Site URL in the App Domain Section. You are not required to include something in the App Domain section if you do not want Authentication.