Twitter Bootstrap: icons in button dropdown
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[Here][1] is the link on jsfiddle with some demo. It works well in Chrome and even in IE, but in FF icons get down. How can I fix it without moving them up with negative margins or something like this? I have no ideas why this happens.

![FF][2]


  [1]: http://jsfiddle.net/DjHyQ/
  [2]: http://i.stack.imgur.com/QQFAO.png