注意2020-02-09:该扩展程序目前尚未维护。 当我最终使用Firefox userChrome.css添加时,我放弃了这个: tabs { counter-reset: tab-counter; } tab:nth-child(1) .tab-label::before, tab:nth-child(2) .tab-label::before, tab:nth-child(3) .tab-label::before, tab:nth-child(4) .tab-label::before, tab:nth-child(5) .tab-label::before, tab:nth-c