Hi ! I am new user, learning HTML & CSS, and I wonder the reason for these lines ( Learn More About CSS Pseudo Selectors By Building A Balance Sheet - Step 5&6) :
These are written just before the table tag (with 2019, 2020, 2021 being headers) but hiddened for readers. I bet it concerns script readers, but I really don’t understand how they could use these lines.
Can someone explain the purpose of these lines?