<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
<title></title>
<style type="text/css">
:empty {
background-color:red;
}
/*指定元素中内容为空白时使用的样式*/
</style>
</head>
<body>
<table border="1" cellpadding="0" cellspacing="0">
<tr>
<td>A</td><td>B</td><td>C</td>
</tr>
<tr>
<td>D</td>
<td>E</td>
<td></td>
</tr>
</table>
</body>
</html>
效果如下：