css filter with IE fallback works perfectly on IE 6+

css-gray-filter.css

.gray-hover{
    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"); /* Firefox 10+, Firefox on Android */
    filter: grayscale(100%); /* moz fix */
    filter: gray; /* IE6-9 */
    -webkit-filter: grayscale(100%); /* Chrome 19+, Safari 6+, Safari 6+ iOS */
    opacity: 0.7;
    -webkit-transition: all 0.5s;
    transition: all 0.5s;
}
.gray-hover:hover {
    filter: url("data:image/svg+xml;utf8,<svg xmlns=\'http://www.w3.org/2000/svg\'><filter id=\'grayscale\'><feColorMatrix type=\'matrix\' values=\'1 0 0 0 0, 0 1 0 0 0, 0 0 1 0 0, 0 0 0 1 0\'/></filter></svg>#grayscale");
    filter: none;
    -webkit-filter: none;
    opacity: 1;
}

nice.