The Send Dialog lets people to send content to specific friends. They’ll have the option to privately share a link as a Facebook message, Group post or email.
You should specify a URL, and you can pre-populate a user in the ‘to’ field. The Send Dialog does not require any extended permissions. This Dialog is currently not supported on mobile devices.
Note: Facebook messages is a channel for user-to-user communication, and not for applications to send messages to their users, or encourage users to spam their friends. In general, applications on Facebook should use Requests when communicating in game status (its your turn), inviting people to use an application, or sending messages to multiple people. You should offer the Send Dialog in situations when a user might otherwise send an email.
You can load the same Send Dialog URL using the Facebook JavaScript SDK:
<html xmlns:fb="http://www.facebook.com/2008/fbml">
<body>
<script src="http://connect.facebook.net/en_US/all.js"></script>
<div id="fb-root"></div>
<script>
// assume we are already logged in
FB.init({appId: '123050457758183', xfbml: true, cookie: true});
FB.ui({
method: 'send',
name: 'People Argue Just to Win',
link: 'http://www.nytimes.com/2011/06/15/arts/people-argue-just-to-win-scholars-assert.html',
});
</script>
</body>
</html>