Facebook applications - how to get to know page ID?

Question

With Facebook API, within a custom app added to a fanpage, how do I recognize the fanpage ID?

Here's what I'm trying to achieve:

• user goes to the full-width canvas app, he authorizes himself there and allows the app to add a tab to one of the fanpages he's administrating
• every Facebook user going to that fanpage, sees the tab and the tab contains content specific to that fanpage (that's why I need to know the fanpage ID)
• if fanpage administrator wants to change something, he goes to the full-width canvas and logs in to my service (here's where I store what he wants to show in his Fanpage)

Answer 1

There are two easy ways to get your fanpage ID:

You have less than 25 fans:

Your fanpage ID is appended to your fanpage URL.
Example: http://www.facebook.com/pages/Social-Media/155188264543525
Your fanpage ID would be: 155188264543525

You have more than 25 fans and have set your vanity URL:

Browse to https://graph.facebook.com/YOURPAGENAME
Example: https://graph.facebook.com/ULTRAGEIL
The first two lines of the output shows:
{
"id": "116645905081622",
Your fanpage ID would be: 116645905081622