Untitled

<!DOCTYPE html>
<html>
<head>

	<title>Homework</title>

	<style type="text/css">
		body{
			background: black;
		}
		#inputhelp{
			font-size: 60px;
			color: white;
		    width: 320px;
		    height: 70px;
		    margin: 0 auto;
		    margin-top: 170px;
		}
		#inputbox{
			width: 185px;
		    height: 20px;
		    margin: 0 auto;
		    margin-top: 20px;
		}
		#yearaccept{
			width: 185px;
		}
		#yearaccept:active{
			background: red;
		}

		#buttonbox{
			width: 185px;
		    height: 20px;
		    margin: 0 auto;
		    margin-top: 10px;
		}
		#futurebox{
			font-size: 50px;
			width: 500px;
			height: 500px;
			border-radius: 3px;
			display: flex;
    		justify-content: center;
    		align-items: center;
    		background: black;
    		color: black;
    		margin: 0 auto;
    		margin-top: 40px;
		}
	</style>

	<script type="text/javascript">
		function save(){
			var text = document.getElementById("inputyear").value;
    		if (text < 2019) {
    			alert('Вы в прошлом')
    	}
    		else if (text >= 2019)  {
				document.getElementById('futurebox').style.color = 'white';
				document.getElementById('futurebox').style.background = '#FF0000';
    		}
    		else{
    			alert('Ошибка! Введите число')
    		}
    }
	</script>

</head>
<body>

	<div id="inputhelp">Введите год</div>
	<div id="inputbox">
		<input id="inputyear" value="">
	</div>
	<br>
	<div id="buttonbox">
		<button id="yearaccept" onclick="save()">Подтвердить</button>
	</div>
	<div id="futurebox"> Back to the Future</div>

</body>
</html>