function set_cookie ( name, value, exp_y, exp_m, exp_d ) {
  var cookie_string = name + "=" + escape ( value );
  if ( exp_y )
  {
    var expires = new Date ( exp_y, exp_m, exp_d );
    cookie_string += "; expires=" + expires.toGMTString();
  }
  document.cookie = cookie_string;
}

function get_cookie ( cookie_name ) {
  var results = document.cookie.match ( '(^|;) ?' + cookie_name + '=([^;]*)(;|$)' );
  if ( results )
    return ( unescape ( results[2] ) );
  else
    return null;
}

function delete_cookie ( cookie_name ) {
	var cookie_date = new Date ( );  // current date & time
	cookie_date.setTime ( cookie_date.getTime() - 1 );
	document.cookie = cookie_name += "=; expires=" + cookie_date.toGMTString();
}