The :nth-child() CSS pseudo-class matches elements based on the indexes of the elements in the child list of their parents. In other words, the :nth-child() selector selects child elements according to their position among all the sibling elements within a parent element....Represents the odd rows of an HTML table: 1, 3, 5, etc. tr:nth-child(even)...Represents the even rows of an HTML table: 2, 4, 6, etc. :nth-child(7)...