Iain M is spot on. You are trying to validate your page as HTML but you are using XHTML specific syntax. If you want your page to validate as valid HTML replace your meta and link tags with:
Code:
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<meta name="keywords" content="Home, Web Development, Budget Web Development, Internet Development, Ecommerce, CMS, SEO">
<meta name="author" content="Ninesquare Systems Ltd.">
<meta name="MSSmartTagsPreventParsing" content="TRUE">
<meta name="resource-type" content="document">
<meta name="distribution" content="Global">
<meta name="rating" content="General">
<meta name="country" content="UK">
<meta name="coverage" content="worldwide">
<meta name="language" content="english">
<meta name="audience" content="all">
<meta name="expires" content="NEVER">
<link rel="stylesheet" type="text/css" href="NS_Includes/CSS/NS_Stylesheet.css" media="screen">
I checked your page using XHTML validation as well and you have more errors but they shouldn't be too hard to fix.