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              <h2>Form 유효성 검사</h2>
<p>이 CodePen을 열면 유효성 검사 오류가 즉시 나타납니다.</p>

    필수입력 <input type="text" name="first-name" required />
  <button type="submit">Submit</button>
              body {
  font-family: '나눔고딕','nanumgothic','돋움','dotum',san-serif;
  color: #333;

form {
  margin-bottom: 10px;
  padding: 6px;
  width: 380px;
  background: #f3f3f3;

input {
  width: 180px;
  vertical-align: middle;
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