function setCookie(NameOfCookie, expiredays) {
var ExpireDate = new Date();
var zipfield = document.getElementById("userzip");
var zipcode = zipfield.value;
ExpireDate.setTime(ExpireDate.getTime() + (expiredays * 24 * 3600 * 1000));
  document.cookie = NameOfCookie + "=" + escape(zipcode) + 
  ((expiredays == null) ? "" : "; expires=" + ExpireDate.toGMTString());
  alert('Starting on your next visit, this page will show a weather forcast for '+zipcode);
}