CSS没有onlclick事件处理程序。您必须使用Javascript。
a:link {color:#FF0000;} /* unvisited link - link is untouched */
a:visited {color:#00FF00;} /* visited link - user has already been to this page */
a:hover {color:#FF00FF;} /* mouse over link - user is hovering over the link with the mouse or has selected it with the keyboard */
a:active {color:#0000FF;} /* selected link - the user has clicked the link and the browser is loading the new page */