function getCookie(name) {
  var dc = document.cookie;
  var prefix = name + "=";
  var begin = dc.indexOf("; " + prefix);
  if (begin == -1) {
    begin = dc.indexOf(prefix);
    if (begin != 0) return null;
  } else {
    begin += 2;
  }
  var end = dc.indexOf(";", begin);
  if (end == -1) {
    end = dc.length;
  }
  return dc.substring(begin + prefix.length, end);
}

function setCookie(name, value, expires) {
  document.cookie = name + "=" + value +
      ((expires) ? "; expires=" + expires.toGMTString() : "");
}

function deleteCookie(name) {
  if (getCookie(name)) {
    document.cookie = name + "=" + 
    "; expires=Thu, 01-Jan-70 00:00:01 GMT";
  }
}