function createCookie(name, value, minutes){
  if (minutes) {
    var date = new Date();
    date.setTime(date.getTime() + (minutes * 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);
}