<div class="tab-group">
  <div class="tab-item is-active">会員情報</div>
  <div class="tab-item">お気に入り</div>
  <div class="tab-item">閲覧履歴</div>
</div>
.tab-group{
  margin-left: auto;
  margin-right: auto;
  max-width: 640px;
  width: 100%;
  height: auto;
  display: flex;
  flex-wrap: wrap;
  justify-content: flex-start;
  align-items: flex-end;
}

.tab-item{
  margin-bottom: 10px;
  flex: auto;
  min-width: 80px;
  padding: 10px 8px;
  text-align: center;
  background: #333;
  font-size: 16px;
  color: #fff;
  border-top: none;
  border-left: none;
  border-right: none;
  border-bottom: solid 3px #888;
  border-top-left-radius: 8px;
  border-top-right-radius: 8px;
  
}

.tab-item.is-active{
    background: #fff;
    color: #333;
    border-top: solid 3px #888;
    border-left: solid 3px #888;
    border-right: solid 3px #888;
    border-bottom: none;
    font-weight: bold;
    font-size: 20px;
}

External CSS

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External JavaScript

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