How To Block Spammers From Your Facebook Page

Here are a few tips on blocking spammers from your Facebook Page.

Make a note of the web address of the SPAM site

Hover over the spam, click on the arrow to the right of it, Mark As Spam.
Then, click on the arrow again and choose Delete. Choose Delete and Ban User.

Up at the top, click on Edit Page, Manage Permissions.
Go down to Moderate Permissions
Type in the core of the address you took note of earlier (example: address.com), and, Save Changes.
Now, anyone (from any Facebook account) trying to spam you with that site will not be able to.

The above info is from this brief video by Mike Mueller.