fix #304: Previewing a protip in firefox doesn't hide back of the card
fix #304: Previewing a protip in firefox doesn't hide back of the card

AVGP/coderwall,sekouzed/coderwall,agileknight/coderwall,pushkar-mishra/coderwall,pushkar-mishra/coderwall,trinitronx/coderwall,ronaldotijucas/coderwall,coderwall/coderwall,seuros/coderwall,alouanemed/coderwall,sekouzed/coderwall,coderwall/coderwall,ggaabe/coderwall,frootloops/coderwall,alouanemed/coderwall,assemblymade/coderwall,pombredanne/coderwall,santoshdeshpande/coderwall,AVGP/coderwall,coderwall/coderwall,agileknight/coderwall,agileknight/coderwall,trinitronx/coderwall,ronaldotijucas/coderwall,wiserfirst/coderwall,pushkar-mishra/coderwall,pombredanne/coderwall,pushkar-mishra/coderwall,santoshdeshpande/coderwall,alouanemed/coderwall,DylanKojiCheslin/coderwall,assemblymade/coderwall,seuros/coderwall,alouanemed/coderwall,pombredanne/coderwall,seuros/coderwall,DylanKojiCheslin/coderwall,ggaabe/coderwall,assemblymade/coderwall,santoshdeshpande/coderwall,DylanKojiCheslin/coderwall,trinitronx/coderwall,wiserfirst/coderwall,frootloops/coderwall,seuros/coderwall,wiserfirst/coderwall,pombredanne/coderwall,trinitronx/coderwall,sekouzed/coderwall,AVGP/coderwall,wiserfirst/coderwall,agileknight/coderwall,ggaabe/coderwall,frootloops/coderwall,assemblymade/coderwall,ronaldotijucas/coderwall,sekouzed/coderwall,coderwall/coderwall,ronaldotijucas/coderwall