function createCookie(name, value, days) {
  if (days) {
    var date = new Date();
    date.setTime(date.getTime()+(days*24*60*60*1000));
    var expires = "; expires="+date.toGMTString();
  } else {
    var expires = "";
  }
  document.cookie = name + "=" + value + expires + "; path=/";
  }
  
function readCookie(name) {
  var nameEQ = name + "=";
  var ca = document.cookie.split(';');
  for (var i = 0; i < ca.length; i++) {
    var c = ca[i];
    while (c.charAt(0) == ' ') {
      c = c.substring(1,c.length);
    }
    if (c.indexOf(nameEQ) == 0) {
      return c.substring(nameEQ.length,c.length);
    }
  }
  return null;
}

function eraseCookie(name) {
  createCookie(name, "", -1);
}