When You are working with facebook apps, you do need sometimes to add administrators or moderators to Your application. If selected person is not in Your friend list, You cannot add him to the list using auto-suggest box. Thats the moment, when You will need to know user`s facebook profile id (uid). Real problem is coming when user is using Facebook vanity URL for his/her profile (like www.facebook.com/some.selected.vanity.url).
The easiest way, how to get his/her UID is to load user`s facebook profile and right click his/her main profile image and select Inspect element in submenu. It will open Your Firebug or browser/DOM inspector (new Firefox or Chrome). In the inspector, You should see and URL of image. What I found out, is, that user`s facebook profile ID is second number in the photo name. Mine was like this: 157184_1317732574_574480779_n.jpg
If You are using Facebook timeline, You could check Facebook profile ID also from the bigger profile picture. In my case it was third number: 425232_3326820732162_1317732574_3347250_1064723857_n.jpg
The easiest way, how to check, if the number is correct is to add selected number behind this URL and load it in the broswer:
If You will want to add more moderators or admins into Your facebook app using these IDs, just find out all of them and insert them into text input separated with comma without spaces. Facebook will handle this numbers and it will add selected profiles into the list of moderators automatically (than just hit Save button at the bottom of the moderation setup dialog/page).
Hope it will help You 😉