Ajax chybka

function ajaxFunction(a,b)
{
    var xmlHttp;
    try {
        xmlHttp=new XMLHttpRequest();  
    }
      
    catch (e) {
        try {
            xmlHttp=new ActiveXObject("Msxml2.XMLHTTP");
        }
        catch (e) {
            try {
                xmlHttp=new ActiveXObject("Microsoft.XMLHTTP");
            }
            catch (e) {
                alert("Nepodporuje AJAX");
                return false;
            }   
        }  
    }
    xmlHttp.onreadystatechange=function() {
        if(xmlHttp.readyState==4) {
            if(xmlHttp.responseText=="kick"){
            alert(xmlHttp.responseText);
            parent.location.href = "../welcome.php?msg=10";
            }else{
            var body = document.getElementsByTagName('body')[0];
            body.innerHTML = xmlHttp.responseText;
        }
        }
    }
    xmlHttp.open("GET",b+".php?rid="+a,true); //php subor
    xmlHttp.send(null); 
}

function runTimer(a,b) {
  window.setInterval("ajaxFunction('"+a+"','"+b+"');", 5000);    //interval refreshu... 1000 = 1 sekunda
}