function GenerateID()
{
  var now = new Date();
  var randomInt = Math.floor(1000000*Math.random());
  return now.getTime() + "_" + randomInt;
}

function setVisitorid()
{
  var oldvisitorid = GetCookie("vid");
  var newvisitorid;
  var now = new Date();
  var oneYear = 365*24*60*60*1000;
  var expireDate = new Date;
  expireDate.setTime(now.getTime() + oneYear);

  if(oldvisitorid)
  {
    newvisitorid = oldvisitorid;
  }
  else
  {
    newvisitorid = GenerateID();
  }
  SetCookie("vid", newvisitorid, expireDate);
}