html {
  filter: progid:DXImageTransform.Microsoft.BasicImage(grayscale=1); 
  filter: grayscale(100%);
  -webkit-filter: grayscale(100%);
  -moz-filter: grayscale(100%);
  -ms-filter: grayscale(100%);
  -o-filter: grayscale(100%);
  filter: gray;
  -webkit-filter: grayscale(1);
}