function getDomain(str) {
     var x = str.split('/');
     x.length = 3;
     return(x.join('/').toLowerCase());
}

function setReferrer() {
     if(getDomain(document.location.href) != getDomain(document.referrer)) {
          document.cookie = 'referrer' + '=' + document.referrer;
     }
}

function getReferrer() {
     var cookies = document.cookie
     if (cookies.indexOf('referrer') != -1) {
          var startpos = cookies.indexOf('referrer') + 'referrer'.length+1;
          var endpos = cookies.indexOf(";",startpos)-1;
          if (endpos == -2) endpos = cookies.length;
          return unescape(cookies.substring(startpos,endpos));
     } else {
          return null;
     }
}

setReferrer()