Refreshing page to keep session

[dc_jt]

Hi I am using the code below to refresh a page using javascript and ajax so that a user is never kicked out however I have had one user say they were kicked out. Is there any reason why their session may have expired? Could it be anything to do with their browser such as they dont have javascript enabled maybe?

 

function Ajax()
{
this.toString = function() { return "Ajax"; }

this.makeRequest = function(_method, _url)
{
	this.request = (window.XMLHttpRequest) ? new XMLHttpRequest() : new ActiveXObject("MSXML2.XMLHTTP");
	this.request.open(_method, _url, true);
	this.request.send(_url);
}

this.checkReadyState = function(_id, _1, _2, _3)
{	
	switch (this.request.readyState)
	{
		case 1:
			if (_id != null) document.getElementById(_id).innerHTML = _1;
			break;
		case 2:
			if (_id != null) document.getElementById(_id).innerHTML = _2;
			break;
		case 3:
			if (_id != null) document.getElementById(_id).innerHTML = _3;
			break;
		case 4:
			return this.request.status;
	}
}
}

var oAjax = new Ajax();
var limit = 0;

function ajaxRefresh()
{
  if (limit==1)
  {
    //make background request
    oAjax.makeRequest('GET', '/sessionrefresh.php');
    limit = iMinutes * 60 + iSeconds;
  }
  else
  {
    limit--;
  }
  setTimeout("ajaxRefresh()",1000)
}

function beginAjaxRefresh()
{
  limit = iMinutes * 60 + iSeconds;
  setTimeout("ajaxRefresh()",1000)
}

var iMinutes = 5;
var iSeconds = 0;
beginAjaxRefresh();

[xenophobia]

what code you've written on your sessionrefresh.php?