looking at the source of your checkout page, there are a number of problems I see, the first seams to be a problem in your template.
at the very top, there are 2 doctype and HTML tags:
<!DOCTYPE html>
<html>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
there should only be one.
further down, there is an opening head tag, then another opening head tag with out a closing head tag:
!-- InstanceBegin template="/Templates/grid.dwt" codeOutsideHTMLIsLocked="false" --><head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Untitled Document</title>
<script src="webassist/progress_bar/jquery-blockui-formprocessing.js" type="text/javascript"></script>
<link href="webassist/forms/fd_newfromblank_default.css" rel="stylesheet" type="text/css" />
<link rel="stylesheet" href="webassist/jq_validation/Bloom.css" />
<script src="//ajax.googleapis.com/ajax/libs/jquery/1/jquery.min.js"></script>
<script src="//ajax.googleapis.com/ajax/libs/jqueryui/1/jquery-ui.min.js"></script>
<link href="WA_eCart/CSS/eC_Checkpoint_Custom_Arial.css" rel="stylesheet" type="text/css" />
<link href="webassist/forms/fd_cool_default.css" rel="stylesheet" type="text/css" />
<link rel="stylesheet" href="webassist/jq_validation/Midnight.css">
<link href="webassist/forms/fd_cool101_default.css" rel="stylesheet" type="text/css" />
<style type="text/css">
@import url("css/main.css");
</style>
<head><a name="backup"></a>
there should be only 1 opening head tag.
the closing head tag is down the page by the body:
</head>
<body class="products_results">
the opening head tag in the middle needs to be removed.
also, there are multiple code blocks for the jquery validation. This suggests that you ran the checkout wizard multiple times. If you need to re runn the checkout wizard, you should first delete the checkout pages to prevent duplicate code from being added.
all the duplicate code is causing conflicts and causing the validation on the page to fail.
Delete the existing checkout pages and rerun the checkout wizard to recreate them, and edit the template to remove the duplicate HTML tags.
