<!doctype html>
<html>
	<head>
		<title>Chat</title>
		<link rel="stylesheet" type="text/css" href="/css/style.css"/>
	</head>
	<body>
		<div id="sidebar">
			<ul id="users"></ul>
		</div>
		<div id="chat-window">
			<ul id="messages"></ul>
		</div>
		<form action="">
			<input id="m" autocomplete="off" />
			<button type="button" id="submit">Send</button>
		</form>
		<script src="/socket.io/socket.io.js"></script>
		<script src="http://code.jquery.com/jquery-1.11.1.js"></script>
		<script src="/javascripts/script.js"></script>
	</body>
</html>

<!doctype html>
<html>
	<head>
		<title>Chat</title>
		<link rel="stylesheet" type="text/css" href="/css/style.css"/>
	</head>
	<body>
		<div id="sidebar">
			<ul id="users"></ul>
		</div>
		<div id="chat-window">
			<ul id="messages"></ul>
		</div>
		<form action="">
			<input id="m" autocomplete="off" />
			<button type="button" id="submit">Send</button>
		</form>
		<script src="/socket.io/socket.io.js"></script>
		<script src="http://code.jquery.com/jquery-1.11.1.js"></script>
		<script src="/js/script.js"></script>
	</body>
</html>

Fix path to script.js in script tag
Fix path to script.js in script tag
