https://purengom.com/2011/05/29/%ed%91%b8%eb%a5%b8%ea%b3%b0-facebook-%ed%8e%98%ec%9d%b4%ec%a7%80%eb%a5%bc-%ea%b0%9c%ec%84%a4%ed%96%88%ec%8a%b5%eb%8b%88%eb%8b%a4/