Odd child:
tr:nth-child(odd) { background-color:wheat; }

1 one
2 two
3 three
4 four
5 five

Even child:
tr:nth-child(even) { background-color:wheat; }

1 one
2 two
3 three
4 four
5 five

Every third child:
tr:nth-child(3n+1) { background-color:wheat; }

1 one
2 two
3 three
4 four
5 five
6 six
7 seven
8 eight
9 nine
10 ten

First child:
tr:first-child { background-color:wheat; }

1 one
2 two
3 three
4 four
5 five

Last child:
tr:last-child { background-color:wheat; }

1 one
2 two
3 three
4 four
5 five

First 3 children:
tr:nth-child(-n+3) { background-color:wheat; }

1 one
2 two
3 three
4 four
5 five

Last 3 children:
tr:nth-last-child(-n+3) { background-color:wheat; }

1 one
2 two
3 three
4 four
5 five

Test of adjacent selector.

This paragraph must be red.

And this must not.

This must be black.