Whats wrong with this AJAX

[dineshswamy]

i ve worked on this script for more than a week but couldnt find out whats wrong with this . please help me out

var c;
function start()
{
window.setInterval("Requestvisits();",1000);
}
function Requestvisits()
{
var xmlHttpobject;
if(window.XMLHttpRequest())
{
c=new XMLHttpRequest();
}
else if(window.ActiveXObject)
{
c=new window.ActiveXObject("Microsoft.XMLHTTP");
}
if(c)
{
c.open("GET","http:172.16.2.147:8080/cs2k9a23/servlet/hform",true);
c.onreadystatechange=function checkvisits()
{
updatevisits();
};
c.send(null);
}
}

function updatevisits()
{
if(c.readyState==4 && c.status=200)
{
var d=document.getElementById("visit");
d.innerHTML=c.responseXML;
}
}

The backend is Servlet .