Action Links
From Facebook Developer Wiki
An action link is a short string of text that accompanies a Feed story and invites the user to take some action related to that story. An action link is a hyperlink to a URL on Facebook or your website or another third-party website. Feed stories can contain only one action link with a maximum length of 25 characters.
Do not use periods (.) or exclamation points (!) in the action link, as Facebook strips out such characters.
Placement of the action link depends on the story size and whether or not the story has comments.
Formatting an Action Link
You specify your action link in a JSON-encoded array, like this:
When using the JavaScript Client Library (for Facebook Connect and IFrame applications), format the array like this:
You include this array in the action_links parameter when you call the stream publishing methods:
Action Link Guidelines
Please read and follow the guidelines and policies for action links.
