A script which sets the cookie

cookieSettingScript

<script>
 
 var cookieName = "visitorFromAdwords"; // Name of your cookie
 var cookieValue = "true"; // Value of your cookie
 var expirationTime = 2592000; // One month in seconds
 expirationTime = expirationTime * 1000; // Converts expirationtime to milliseconds
 var date = new Date(); 
 var dateTimeNow = date.getTime(); 

 date.setTime(dateTimeNow + expirationTime); // Sets expiration time (Time now + one month)
 var expirationTime = date.toUTCString(); // Converts milliseconds to UTC time string
 document.cookie = cookieName+"="+cookieValue+"; expires="+expirationTime+"; path=/; domain=." + location.hostname.replace(/^www\./i, ""); // Sets cookie for all subdomains

</script>