What does @ in css mean?

Question

For the first time I see this. I could not find anything. Saw it in twitter bootstrap

Jeremen1

651 2 gold marks 14 silver marks 42 bronze marks

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1 answer 1

Zhukov Roman Zhukov Roman 8,890 10 silver marks 26 bronze marks · Accepted Answer · 2013-03-07T09:56:24

Answer 1 , answer 2 (official). How were you looking ?? Googles in five seconds.