Methods for making websites turn gray or black (National Mourning Day)

On May 19-21, 2009, a national day of mourning was held for the Wenchuan Earthquake. On April 21, 2010, another national day of mourning was observed for the Yushu Earthquake in Qinghai. During the 2009 national day of mourning, apart from major newspapers and media outlets using black-and-white pages to convey a sense of shock, it was particularly heartening to see websites of all sizes switch to a black-and-gray style to express deep condolences for the compatriots who lost their lives in the earthquake. Leesum shares several types of gray-black CSS filter codes so that we can all pray sincerely and offer blessings for the victims through concrete actions.