JSFiddle - React, Tailwind, and code Playground

HTML

<!DOCTYPE html>
<head>
<title>My Site</title>
</head>
<body>
<div id="wrapper">    <div id="header">
    <ul id="login_register">
        <li><a href="sign_in.php">Login</a></li>
        <li>|</li>
        <li><a href="register.php">Register</a></li>
    </ul>
    <h1>Welcome to My Site!</h1>
    <ul id="navbar">
        <li><a href="index.php">HOME</a></li>
        <li>NUM 2</li>
        <li>NUM 3</li>
    </ul>
</div><!--header-->    
    <div id="content">
        <div id="main_pic" class="main_div">
        THIS IS WHERE THE MAIN PIC WILL GO.
        </div>
        <div id="signin" class="main_div">
            SIGN IN TO THE SITE!
            <form>
                <label for="name">EMAIL/USERNAME:</label>
                <input type="text" name="name" id="name">
                <label for="email">PASSWORD:</label>
                <input type="text" name="email" id="email">
                <br />
                <input type="submit" value="Let's Play!">
            </form>
        </div>
    </div>
    </div><!--wrapper-->
</body>
</html>

CSS

*{
margin:0;
padding:0;
}

body{
margin-bottom:50px;
width:960px;
margin:0 auto;
}

#wrapper{
width:960px;
border:1px solid black;
margin:0 auto;
}

/*******START HEADER********/

#wrapper #header{
height:170px;
border:1px solid black;
}

#wrapper #header ul{
list-style-type:none;
}

#wrapper #header ul li{
float:left;
padding:5px 10px 10px 5px;
}

#wrapper #header #navbar{
margin:0 0 0 10px;
}

#wrapper #header h1{
height:100px;
padding:20px;
}

#login_register{
float:right;
}

/*******END HEADER********/

/*******START MAIN CONTENT********/
#wrapper #content{
height:550px;
}

#wrapper #content .main_div{
height:400px;
}

#wrapper #content #main_pic{
width:620px;
height:500px;
margin:20px;
border:1px solid black;
}

#wrapper #content #signin{
width:250px;
height:300px;
border:1px solid black;
margin:20px;
}

#wrapper #content #signin form{
margin-top:30px;
}

#wrapper #content #signin form input, #wrapper #content #signin form label{
margin:10px;
font-size:18px;
}

#wrapper #content p{
padding:20px;
}

/*******END MAIN CONTENT********/