iFrame in facebook pages

Hi.I am trying to create a fan page for my facebook page.But the settings are not working properly.Can anyone tell me what is App Domain and Page Tab URL?The page is hosted on mydomain.com/facebook.Please help me.

A lot of businesses are missing out on a great opportunity by not having a custom landing page for their Facebook fan page. Most Facebook pages look the same in design and layout.

Yes.Its true that facebook keeps changing the layout and they have stopped using fbml now.But iFrame seems more easy than fbml.I resolved the issue and now my fan page is working like magic.Just needed to put a site url at website section.<snip>