Im trying to implement a basic 3 Column Layout w/ XHTML+CSS

I cant figure out why but the browser doesnt even make an attempt to request 'Default.css' (i know via IIS Logs)

I tried both IE6 and FireFox 0.9.3

HTML:
Code:
<?xml-stylesheet href="Default.css" type="text/css"?>
<!DOCTYPE html
PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<HTML xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
	<HEAD>
		<title>Default</title>
	</HEAD>
	<body>
		<div id="container">
			<form id="main" runat="server">
				<div id="pageheader">Header</div>
				<div id="pageleftcolumn">Left Column</div>
				<div id="pagerightcolumn">Right Column</div>
				<div id="pagecentercolumn">Center Column</div>
				<div id="pagefooter"></div>
			</form>
		</div>
	</body>
</HTML>
CSS:

Code:
#container{
width:750px;
margin-left:auto;
margin-right:auto;
background:yellow;
border:1px solid #fff000;
}
#pageheader {
background:red;
border:1px solid #000;
margin:10px 0;
}
#pageleftcolumn, #pagecentercolumn, #pagerightcolumn {
float:left;
width:248px;
background:green;
border:1px solid #000;
margin-bottom:10px;
}
#pagecentercolumn {background:blue;}
#pagerightcolumn {background:pink;}
#pagefooter{
clear:both;
background:#ffffcc;
border:1px solid #000;
margin-bottom:10px;
}