I am using the Facebook like box code in my side bar by pasting the Facebook code into a text widget. My theme is responsive, and I'd like to get the like box to resize correctly. I found this tutorial but he says the way he is doing it, isn't "fully responsive" so I didn't know if there was a better way to do it.
None of the css trick worked for me (in my case the fb-like box was pulled right with "float:right"). However, what worked without any additional tricks is an IFRAME version of the button code. I.e.:
<iframe src="//www.facebook.com/plugins/like.php?href=..."
scrolling="no" frameborder="0"
style="border:none; overflow:hidden; width:71px; height:21px;"
allowTransparency="true">
</iframe>
(Note custom width in style, and no need to include additional javascript.)