var req=null;

function GetXMLHttpRequest(callback,url)
{
      {
        if(window.XMLHttpRequest)
        { 
         
            req=new XMLHttpRequest();
            req.onreadystatechange=callback;
          
            req.open("GET",url,true);
            req.send(null);
           
         }
         else if(window.ActiveXObject)
         {
            try{
            
                req=new ActiveXObject("Msxml2.XMLHTTP");
                req.onreadystatechange=callback;
                req.open("GET",url,true);
                req.send();
               }
            catch(e){}
            if(req==null)
            {
             try{
            
                req=new ActiveXObject("Microsoft.XMLHTTP");
                req.onreadystatechange=callback;
                req.open("GET",url,true);
                req.send();
            }
            catch(e){}
                
            }
         }
         if(req==null)
        
            alert("Your browser does not support this function!")
         }
         
    }
    function ProcessRequest()
    {
        if(req.readyState==4)
        {
            if(req.status==200)
            {
                var result=req.responseText;
                if(result)
                {
                    //document.write(result);
                }
            }
            else
            {
                alert("An error has happen"+req.statusText);
            }
        }
       
    }
    function ClearSession()
    {
        var url="/ClearSession.aspx";
        var callback=ProcessRequest;
       
        GetXMLHttpRequest(callback,url);
        
    }