Gray out the page

Set the following code on html to set the page to gray

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