Fb force mode
From Facebook Developer Wiki
fb_force_mode is a GET (or query-string based) parameter that can be added to your Facebook application to force it to be rendered as an iframe or FBML application, depending on what you choose.
For example, if you were using an iframe application, and wanted one page to be rendered as FBML, you could append ?fb_force_mode=fbml to the address, which will cause it to render as FBML. This can be particularly useful when using fb:request-form with iframe applications.
If your application is an iframe application and you wish to use FBML, you will need to specify the full address, including http://apps.facebook.com.
