The minimum skin requirements for a version 7 skin are displayed. Each skin needs a base number of PHP/HTML tags to be valid, and this article provides that information.
<?php $skinfunc =& $this->include_skinfunc('CORE_SkinFunc'); ?>
<!DOCTYPE html PUBLIC "-//W3CDTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="content-type" content="text/html; charset=ISO-8859-1" />
<meta name="keywords" content="<?php print $metakeywords; ?>" />
<meta name="description" content="<?php print $metadesc; ?>" />
<?php $skinfunc->robotstag(); ?>
<base href="<?php print $disp_baseurl; ?>" />
<link rel="stylesheet" type="text/css" media="all" href="skins/SKIN_NAME_HERE/css/all.css" />
<?php $skinfunc->xnamespace('core','jslib'); ?>
<title><?php print $metatitle; ?></title>
</head>
<body>
<?php $skinfunc->content(); ?>
<?php $skinfunc->debug(); ?>
</body>
</html>
