html {
  filter: grayscale(100%);
  -webkit-filter: grayscale(100%);  /* Chrome, Safari, Edge */
  -moz-filter: grayscale(100%);     /* Firefox */
  -ms-filter: grayscale(100%);      /* IE 10+ */
  -o-filter: grayscale(100%);       /* Opera 12.1-15 */
  filter: gray;                     /* IE 6-9 */
  filter: progid:DXImageTransform.Microsoft.BasicImage(grayscale=1); /* 旧版IE */
}