https://blog.faceutil.com/2020/05/28/%eb%b9%84%ed%91%9c%ec%a4%80-%eb%aa%a8%eb%93%9cquirks-mode-%ed%91%9c%ec%a4%80-%eb%aa%a8%eb%93%9c-standards-mode-%ec%b0%a8%ec%9d%b4%ec%99%80-doctype-s/