SOURCE

<div class="demo">
    <label><em>*</em><span>昵称</span>：</label><input type="text" style = 'width: 100px'>
    <br><br><br><br>
    <em>*</em><span>电子邮箱</span>：<input type="email" style = 'width: 100px;'>
</div>

em {
  float: left;
}

span {
  width: 100px;
  border: 1px solid red;
  text-align: justify;
  /* text-justify:inter-ideograph; // 兼容ie */
  /* text-align-last:justify;  // 兼容ie（但必须在文字之间敲空格） */
  float: left;
  margin-left: 10px;
}

span:after {
  content: '';
  width: 100%;
  display: inline-block;
}

input {
  width: 100px;
}