varArray = document.location.href.split('?')[1].split('&');
for(var x=0; x<varArray.length; x++)
{
    var tmp = varArray[x].split('=');
    if(tmp[0] == "visit_id") {
       var date = new Date();
       expire = date.setTime(date.getTime()+(7*24*60*60*1000));
       document.cookie = 'visit_id=' + tmp[1] + ';expires='+ expire + ';path=/'
    }
}