HTML, BODY {
	height: 100%;
}
#login_div, #logout_div {
	position: absolute;
	top: 50%;
	left: 50%;
	transform: translate(-50%,-50%);
}

#login_logo {
	width: 50%; 
	margin: 0 auto 30px;
	display: block;
}
#login_form {
	min-width: 250px;	
}