How do you add FBConnectButton?

I see several websites such as macrumors.com using a Facebook button that is dark blue with their facebook logo and the word share on it... looking at code it says its called FBConnectButton, but a google search for it turns up not开发者_开发知识库hing useful, nor is it obvious on the Facebook website.

This post refers to it as well, but not where the code originated from:

How to modify the facebook share button?

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That's the old fb:share-button, you should probably be using fb:like these days, as fb:share-button has been phased out.