Basically you put set_cookie in the wrong place, any modification made to cookies, for example, session_start, or set_cookie must be done before http header is sent to the client. After the header is sent you can read cookies but not set them.
To fix it, move your php code
<?php
$url="COOKIES";
setcookie ("visitor_", "", time()-3600);
setcookie ('visitor_', $url, time() + (60*60*24),'/','.abcde.com');
?>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<title>Untitled Document</title>
<style type="text/css">
</style>
</head>
<body>
</body>
</html>