Hi, personally I use a css class like that:
/* grayscale*/
img.grayscale{
filter: grayscale(100%);
-webkit-filter: grayscale(100%); /* For Webkit browsers */
filter: gray; /* For IE 6 - 9 */
-webkit-transition: all .6s ease; /* Fade to color for Chrome and Safari */
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 */
}
img.grayscale:hover{
filter: grayscale(0%);
-webkit-filter: grayscale(0%);
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");
}
It works with every browser (not that I tried them all though), and it's simple and quick.
/* grayscale*/
img.grayscale{
filter: grayscale(100%);
-webkit-filter: grayscale(100%); /* For Webkit browsers */
filter: gray; /* For IE 6 - 9 */
-webkit-transition: all .6s ease; /* Fade to color for Chrome and Safari */
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 */
}
img.grayscale:hover{
filter: grayscale(0%);
-webkit-filter: grayscale(0%);
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");
}
It works with every browser (not that I tried them all though), and it's simple and quick.