No, it is about marking up the data (HTML) with labels that have a representation described in the CSS. So the HTML should say "this is important" (em) while t

No, it is about marking up the data (HTML) with labels that have a representation described in the CSS. So the HTML should say "this is important" (em) while the CSS is free to define "important" as bold, different color or some other font change. For example the HTML should not contain anything about number of columns. It will be 1 column on iPhone, 2 on iPad and 4 on Desktop - but the HTML does not change.