Matches elements that have no children, including other elements or text. Comments are ignored, although any amount of whitespace will negate a match.
Syntax
As a structural pseudo-class selector, empty is preceded by a colon (:). To make it element specific, you can place a simple selector prior to the colon with no whitespace.
:empty {
border: 1px solid red;
}
td:empty {
border: 1px solid red;
}