CSS entire page grayed tone

Because the new crown pneumonia epidemic, the State Council issued: a national day of mourning on April 4
for the expression of people of all nationalities to fight against the new crown pneumonia epidemic struggle and sacrifices of the martyrs deep condolences to the death, the State Council decided to hold a national 2020 April 4 mourning. In the meantime, national and foreign embassies and consulates to half-mast mourning, to stop public entertainment nationwide. Starting at 10:04 on April, the National People's silence for three minutes, cars, trains, ships whistle, air raid sirens.

In order to express condolences, the site will become gray tones throughout the site.

css implementation code may refer to the following:

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);
}