JSFiddle - React, Tailwind, and code Playground

HTML

<meta charset="UTF-8">
 <link type="text/css" rel="stylesheet" href="stylesheet.css"/>
 <body>
	<div id="container"><!---container--->
<div id="header">
<h1>JORDAS</h1>

</div><!--header-->

<div id="nav">
<a href="index.html">Etusivu</a> <br>
<a href="teltat.html">Teltat</a><br>
<a href="page2.html">Palvelut</a><br>
<a href="Yhteystiedot.html">Yhteistiedot</a><br>
</div>

<div id="section">


<div class="main_block">

<p> Tervetuloa Jordas Ab:n kotisivuille. Olemme...

</div><!--mainblock-->
</div>

<div id="footer">
<h3>POP-UP TELTTOJEN YKKÖNEN </h3>
	</div><!--footer-->
</div> <!--container-->
</body>

CSS

<style>

body{margin:0;
	padding:0;
	}
 #header {
    background-color:#ff6600;
    color:white;
    text-align:left;
    padding:2px;
 }

#nav {
    line-height:30px;
    background-color:#fff000;
    height:350px;
    width:125px;
    float:left;
    padding:5px;

}
#section {
    width:350px;
    float:left;
    padding:10px;
}
#footer {
    background-color:#737373;
    color:white;
    clear:both;
    text-align:center;
    
	
}
#container {
	margin:auto;
	width:900px;
	text-align:left;
	overflow: hidden;

}
.inner_block {
  display: inline-block;
  text-align: center;
  width: 350px;
  height:200px;
 

}

img {
  width: 350px;
}

.main_block{
  text-align:center;
  width:750px;

}
</style>