img.scaladigrigi {
    filter: url("data:image/svg+xml;utf8,#grayscale"); /* Firefox 10+, Firefox on Android */
    filter: gray; /* IE6-9 */
    -webkit-filter: grayscale(100%); /* Chrome 19+, Safari 6+, Safari 6+ iOS */
}

img.scaladigrigi:hover {
filter: url("data:image/svg+xml;utf8,#grayscale");
-webkit-filter: grayscale(0%);
}