The postition:absolute; tag positions the element relative to it's immediate parent.
I noticed that even in the examples, there isn't room for scrolling, and when i tried it out, it didn't work.
Therefore, to pull off the facebook floating menu, the position:fixed; tag should be used instead. It displaces/keeps the element at the given/specified location, and the rest of the page can scroll smoothly - even with the responsive ones.
Please see CSS postion attribute documentation when you can :)