E:only-child From CSS3 previous page next page CSS参考手册 » 选择符列表 » 伪类选择符 » 相关内容： 其它伪类选择符参考 选择其它项 E:link E:visited E:hover E:active E:focus E:lang() E:not() E:root E:first-child E:last-child E:only-child E:nth-child(n) E:nth-last-child(n) E:first-of-type E:last-of-type E:only-of-type E:nth-of-type(n) E:nth-last-of-type(n) E:empty E:checked E:enabled E:disabled E:target @page:first @page:left @page:right 结构性伪类选择符 E:only-child 版本：CSS3