html, .btl_grayscale {
/* Modern browsers */
  filter: grayscale(100%) !important;
  
  /* Webkit browsers (Chrome, Safari, Edge) */
  -webkit-filter: grayscale(100%) !important;
  
  /* Firefox */
  -moz-filter: grayscale(100%) !important;
  
  /* IE 6-9 */
  filter: gray !important;
  
  /* Edge HTML (Old Edge) */
  -ms-filter: "progid:DXImageTransform.Microsoft.BasicImage(grayscale=1)" !important;
  
  /* Opera */
  -o-filter: grayscale(100%) !important;
}