.grayscale {
    -webkit-filter: grayscale(100%);
    -moz-filter: grayscale(100%);
    -ms-filter: grayscale(100%);
    -o-filter: grayscale(100%);
    filter: grayscale(100%);
    /*Firefox 4+*/
    /*filter: url(./grayscale.svg#greyscale);*/
    /*IE 6-9*/
    filter: gray;
    -webkit-transition: all 0.3s ease;
    -moz-transition: all 0.3s ease;
    -o-transition: all 0.3s ease;
    -ms-transition: all 0.3s ease;
    transition: all 0.3s ease;
}

.grayscale:hover {
    -webkit-filter: grayscale(0%);
    -moz-filter: grayscale(0%);
    -ms-filter: grayscale(0%);
    -o-filter: grayscale(0%);
    -webkit-transition: all 0.3s ease;
    -moz-transition: all 0.3s ease;
    -o-transition: all 0.3s ease;
    -ms-transition: all 0.3s ease;
    transition: all 0.3s ease;
    filter: none;
}