React - Login on Center of Page

react-login-center.jsx

const centerLogin = {
    'position': 'fixed',
    'top': '50%',
    'left': '50%',
    'margin-top': '-100px',
    'margin-left': '-200px'
};

return (
    <section className="container">
        <Helmet>
            <title>Sign in</title>
        </Helmet>
        <div className="container" style={centerLogin}>
            {/* <h1 className="page-header">Sign in</h1> */}
            <div className="row">
                <div className="col-sm-4">
                    <div className="panel panel-default">
                        {/* <div className="panel-heading">Login</div> */}
                        <div className="panel-body">
                            <form onSubmit={this.handleSubmit.bind(this)}>
                                {alerts}
                                {formElements}
                            </form>
                            <h5>*Please use SDM Online Credentials</h5> 
                        </div>
                    </div>
                </div>
            </div>
        </div>
    </section>
);