function createCookie(cname,cvalue,cdays) {
 if (cdays) {
  var date = new Date();
  date.setTime(date.getTime() + (cdays*24*60*60*1000));
  var expires = "; expires = "+ date.toGMTString();
 }
 else var expires = "";
 document.cookie = cname + "="+ cvalue + expires + "; path=/";      // available throughout the directory
}

function readCookie(cname) {
 var nameEQ = cname + "=";
 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(cname) {
 createCookie(cname,"",-1);  // set cookie to expire on previous day
}