Почему курсор ниже поля ввода на мобильных устройствах?

<div class="ajaxlogin-form">
   
    <form action="/" method="post" class="form-horizontal" role="form">
        <fieldset>

            <div class="form-group">
                <label for="ajaxlogin-username" class="col-sm-4 control-label">Email</label>
                <div class="col-sm-8">
                    <input type="email" class="form-control" id="ajaxlogin-username" name="username">
                </div>
            </div>

            <div class="form-group">
                <label for="ajaxlogin-password" class="col-sm-4 control-label">Пароль</label>
                <div class="col-sm-8">
                    <input type="password" class="form-control" id="ajaxlogin-password" name="password">
                </div>
            </div>

            <input type="hidden" name="service" value="login">

            <div class="form-group">
                <label class="col-sm-4 control-label"></label>
                <div class="col-sm-8 col-sm-4">
                    <input type="submit" class="btn btn-danger ajaxlogin-action" name="Login" value="Войти">
                </div>
            </div>

        </fieldset>
    </form>
</div>