Selector

:not()

Select But …

:not(.some-class) {
}

:nth-child()

Select Even Elements

:nth-child(even) {
}

E.g., set the background of even lines in tables to be different than that of odd ones.

tr {
    background-color: red;
}

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

Others

Leading zero

To save the CSS file size, 0.5 should be written without a leading zero as .5.