<div class="form-group"> <h2>Please enter the password</h2> <p>Your browser must accept cookies in order to log in.</p> <input type="password" name="password" size="15"> <input type="submit" value="login"> </div> 整个页面上下左右都居中 文本页居中

.form-group {
      position: absolute;
      top:50%;
      left:50%;
      transform: translate(-50%, -50%);
    }