.grayscale {
    /* Firefox 10+, Firefox on Android */
    filter: url("data:image/svg+xml;utf8,<svg xmlns='http://www.w3.org/2000/svg'><filter id='grayscale'><feColorMatrix type='matrix' values='0.3333 0.3333 0.3333 0 0 0.3333 0.3333 0.3333 0 0 0.3333 0.3333 0.3333 0 0 0 0 0 1 0'/></filter></svg>#grayscale");

    /* IE 6-9 */
    filter: gray;

    /* Chrome 19+, Safari 6+, Safari 6+ iOS */
    -webkit-filter: grayscale(100%);
}