Something went wrong here - the code I see for your test page looks like this:
<DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html>
<head>
<title>My Practice HTML Page</title>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<title>First CSS Tutorial</title>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<link href="[url=""]myCSS.css" rel="stylesheet[/url]" type="text/css">
</head>
<body>
<div id="navigation">
<h2>The Main navigation</h2>;
</div>
<div id="centerDoc">
<h1>The Main Heading</h1>
<p>Go to the Web Designer's Killer Handbook home page and grab the practice HTML page that we will used as the starting template for this tutorial. You can find it under the heading: 'To create the practice HTML page do the following:'. Follow the instructions there and create your basic HTML page - and do it now! </p>
</div>
</body>
</html>
It should look like this:
<link href="[url=""]myCSS.css" rel="stylesheet[/url]" type="text/css">
And you have a stray ';" right here:
<h2>The Main navigation</h2>
;
Making these changes should fix things. Let me know.