Here's some code which i just lately wrote. I believe that it provides a basic clarification of combining course/ID names with pseudoclasses. They're all recognised in CSS as at-principles. They are Exclusive Directions for that browser, in a roundabout way associated with styling of (X)HTML/XML factors in Internet files using https://www.presta-addons-modules.com/en/administration/prestashop-back-office-login-geolocation-history-and-statistics-charts.html