CSS代码：
1：

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

2：

html {filter: grayscale(1);
-webkit-filter: grayscale(1);
filter: progid:DXImageTransform.Microsoft.BasicImage(grayscale=1);}

3：

html {
    filter: grayscale(100%);
    -webkit-filter: grayscale(100%);
    -moz-filter: grayscale(100%);
    -ms-filter: grayscale(100%);
    -o-filter: grayscale(100%);

    filter: progid:DXImageTransform.Microsoft.BasicImage(grayscale=1);
    -webkit-filter: grayscale(1);
}

放在调用head.html。