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button.grey span{
background-position: 0 -1px;
}
button.grey:hover span{
background-position: 0 -36px;
}
button.grey:active span{
background-position: 0 -71px;
}
button.grey span{
background-position: 0 0px\9;
}
button.grey:hover span{
background-position: 0 -35px\9;
}
button.grey:active span{
background-position: 0 -70px\9;
}
: http://jsbin.com/orami3/9