Edit in JSFiddle

<form>
  <fieldset class="account-info">
    <label>
      Имя пользователя
      <input type="text" name="username">
    </label>
    <label>
      Пароль
      <input type="password" name="password">
    </label>
  </fieldset>
  <fieldset class="account-action">
    <input class="btn" type="submit" name="submit" value="Войти">
    <label>
      <input type="checkbox" name="remember"> Запомнить
    </label>
  </fieldset>
</form>

*,
*:before,
*:after {
  box-sizing: border-box;
}
form {
  border: 1px solid #c6c7cc;
  border-radius: 5px;
  font: 14px/1.4 "Helvetica Neue", Helvetica, Arial, sans-serif;
  overflow: hidden;
  width: 240px;
}
fieldset {
  border: 0;
  margin: 0;
  padding: 0;
}
input {
  border-radius: 5px;
  font: 14px/1.4 "Helvetica Neue", Helvetica, Arial, sans-serif;
  margin: 0;
}
.account-info {
  padding: 20px 20px 0 20px;
}
.account-info label {
  color: #395870;
  display: block;
  font-weight: bold;
  margin-bottom: 20px;
}
.account-info input {
  background: #fff;
  border: 1px solid #c6c7cc;
  box-shadow: inset 0 1px 1px rgba(0, 0, 0, .1);
  color: #636466;
  padding: 6px;
  margin-top: 6px;
  width: 100%;
}
.account-action {
  background: #f0f0f2;
  border-top: 1px solid #c6c7cc;
  padding: 20px;
}
.account-action .btn {
  background: linear-gradient(#49708f, #293f50);
  border: 0;
  color: #fff;
  cursor: pointer;
  font-weight: bold;
  float: left;
  padding: 8px 16px;
}
.account-action label {
  color: #7c7c80;
  font-size: 12px;
  float: left;
  margin: 10px 0 0 20px;
}