It's simple using a table:
<html>
<head>
<title>100% Height test</title>
</head>
<body>
<table style="float: left; height: 100%; width: 200px; border: 1px solid red">
<tbody>
<tr>
<td>Nav area</td>
</tr>
</tbody>
</table>
<div style="border: 1px solid green;">Content blabla... text
<br /> text
<br /> text
<br /> text
<br />
</div>
</body>
</html>
When DIV was introduced, people were so afraid of tables that the poor DIV became the metaphorical hammer.