a标签怎么去下划线以及实现点击前和点击后不变

a:link {
font-size: 12px;
color: #000000;
text-decoration: none;
}
a:visited {
font-size: 12px;
color: #000000;
text-decoration: none;
}
a:hover {
font-size: 12px;
color: #999999;
text-decoration: underline;
}

<style type="text/css">
<!--
a:link {
font-size: 12px;
color: #000000;
text-decoration: none;
}
a:visited {
font-size: 12px;
color: #000000;
text-decoration: none;
}
a:hover {
font-size: 12px;
color: #999999;
text-decoration: underline;
}
-->
</style>