When the webmaster dont check the ‘Author Credits’ checkbox, the plugin puts an hidden link in the page. Not in the footer, but in the head, You can see the code above.
…
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "https://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="https://www.w3.org/1999/xhtml" dir="ltr" lang="en-US"
xmlns:og="https://opengraphprotocol.org/schema/"
xmlns:fb="https://www.facebook.com/2008/fbml">
<head profile="https://gmpg.org/xfn/11">
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<title>WordPress Portable </title>
<meta name="generator" content="WordPress" /> <!-- leave this for stats -->
<link rel="stylesheet" href="https://localhost/wordpress/wp-content/themes/wp-whiskey-air/style.css" type="text/css" media="screen" />
<link rel="pingback" href="https://localhost/wordpress/xmlrpc.php" />
<link rel='archives' title='September 2012' href='https://localhost/wordpress/2012/09/' />
<link rel='archives' title='June 2010' href='https://localhost/wordpress/2010/06/' />
<meta name='robots' content='noindex,nofollow' />
<link rel="alternate" type="application/rss+xml" title="WordPress Portable ? Feed" href="https://localhost/wordpress/feed/" />
<link rel="alternate" type="application/rss+xml" title="WordPress Portable ? Comments Feed" href="https://localhost/wordpress/comments/feed/" />
<link rel='stylesheet' id='scu-css-css' href='https://localhost/wordpress/wp-content/plugins/site-creator-ultimate/style.css?ver=1.0.0' type='text/css' media='all' />
<script type='text/javascript' src='https://localhost/wordpress/wp-includes/js/jquery/jquery.js?ver=1.7.2'></script>
<link rel="EditURI" type="application/rsd+xml" title="RSD" href="https://localhost/wordpress/xmlrpc.php?rsd" />
<link rel="wlwmanifest" type="application/wlwmanifest+xml" href="https://localhost/wordpress/wp-includes/wlwmanifest.xml" />
<meta name="generator" content="WordPress 3.4.2" />
<style type="text/css">.credits_off {display:none;}</style><a href="https://www.facebooklikebutton.co/">facebooklikebutton.co</a><meta property="og:site_name" content="WordPress Portable" />
<meta property="og:type" content="article" />
</head>