I'm trying to add the Facebook Like Box social plugin in my website(I took the code from the official documentation).
It works fine but only if I'm logged into Facebook; if not it just shows
Facebook Public Profile Login to see this content
I don't really understand the problem because in other websites I've built everything worked just fine.
I'm thinking that this might be a page setting.
This is my <iframe> code for the Like Box:
<iframe src="http://www.facebook.com/plugins/likebox.php?id=1331391XXXXXXXX&width=298&connections=10&stream=false&header=true" scrolling="no" frameborder="0" allowTransparency="true" style="border:none; overflow:hidden; width:298px; height:290px">
If the Like box won't display content to logged-out users, it's almost certainly because there's a demographic restriction on your page. The API (and social plugins) will only return information about such pages to users who meet the restrictions.
It's most likely that you've not yet published the page, have marked the page as being for users >18, for users in a certain country, or have marked the page as being 'Alcohol related' (which limits it to users of legal drinking age in their country)
To solve this issue Just go to edit page and see the left side option "Manage Permission" In that tab set "Age Restrictions:" Anyone 13+. You must also remove any country restrictions. Save it. Now it works
Change your age restrictions to "Anyone 13+" if that is applicable to your fanpage. Just enlarge the image in this post for a detailed walkthrough:
http://www.profromgo.com/facebook-social-plugin-working-logged-users
来源：https://stackoverflow.com/questions/7268100/facebook-like-box-plugin-doesnt-show-up-for-logged-out-users-only-for-logged-i