说明:

匹配属于父元素中唯一子元素的E

兼容性:

类型 IEInternet Explorer FirefoxFirefox ChromeChrome OperaOpera SafariSafari
版本 (×)IE6 (×)Firefox 2.0 (√)Chrome 1.0.x (√)Opera 9.63 (√)Safari 3.1
(×)IE7 (√)Firefox 3.0 (√)Chrome 2.0.x (√)Safari 4Public beta
(×)IE8 (√)Firefox 3.5

示例: