页面置灰

<style>
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);
}
</style>