<a href="#!">クリックすると下線が消えるよ</a>
a{
  text-decoration: none;
  border-bottom-width: 1px;
  border-bottom-style: solid;
  border-bottom-color: #333;
  color: #333;
}

a:visited{
  border-bottom-color: transparent;
  color: pink;
}

a:hover{
  border-bottom-color: transparent;
}

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External JavaScript

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