css 全局一键黑白

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