function callAjax(url, func, arg)
{
   var xmlHttp;
   try
   {
      // Firefox, Opera 8.0+, Safari
      xmlHttp=new XMLHttpRequest();
   }
   catch (e)
   {
      // Internet Explorer
      try
      {
         xmlHttp=new ActiveXObject("Msxml2.XMLHTTP");
      }
      catch (e)
      {
         try
         {
            xmlHttp=new ActiveXObject("Microsoft.XMLHTTP");
         }
         catch (e)
         {
            alert("Your browser does not support AJAX!");
            return null;
         }
      }
   }

   xmlHttp.onreadystatechange=function()
   {
      if(xmlHttp.readyState==4)
      {
         func(arg, xmlHttp.responseText);
      }
   }
   xmlHttp.open("GET", url, true);
   xmlHttp.send(null);
}