:nth-last-child() – pseudo-class | Selectors Level 3 The :nth-last-child(an+b) works similar to nth-child() pseudo-class. The difference is that :nth-last-child selects elements from bottom of the parent element. It also accepts the “even” and “odd” values as arguments.
:not(s) – pseudo class, negation It takes simple selector “s” as an argument and matches an element that is not represented by this argument (“s”). Argument “s” must not contain another negation selector.
:nth-child(an+b)- pseudo-class The :nth-child(n) is a CSS pseudo-class defined in the Selectors Level 3. It allows you to select one or multiple elements according to their positions in their parent element.